snprintf.c

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/*
 * Copyright (c) 1983, 1995, 1996 Eric P. Allman
 * Copyright (c) 1988, 1993
 *  The Regents of the University of California.  All rights reserved.
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * src/port/snprintf.c
 */
 
#include "c.h"
 
#include <math.h>
 
/*
 * We used to use the platform's NL_ARGMAX here, but that's a bad idea,
 * first because the point of this module is to remove platform dependencies
 * not perpetuate them, and second because some platforms use ridiculously
 * large values, leading to excessive stack consumption in dopr().
 */
#define PG_NL_ARGMAX 31
 
 
/*
 *  SNPRINTF, VSNPRINTF and friends
 *
 * These versions have been grabbed off the net.  They have been
 * cleaned up to compile properly and support for most of the C99
 * specification has been added.  Remaining unimplemented features are:
 *
 * 1. No locale support: the radix character is always '.' and the '
 * (single quote) format flag is ignored.
 *
 * 2. No support for the "%n" format specification.
 *
 * 3. No support for wide characters ("lc" and "ls" formats).
 *
 * 4. No support for "long double" ("Lf" and related formats).
 *
 * 5. Space and '#' flags are not implemented.
 *
 * In addition, we support some extensions over C99:
 *
 * 1. Argument order control through "%n$" and "*n$", as required by POSIX.
 *
 * 2. "%m" expands to the value of strerror(errno), where errno is the
 * value that variable had at the start of the call.  This is a glibc
 * extension, but a very useful one.
 *
 *
 * Historically the result values of sprintf/snprintf varied across platforms.
 * This implementation now follows the C99 standard:
 *
 * 1. -1 is returned if an error is detected in the format string, or if
 * a write to the target stream fails (as reported by fwrite).  Note that
 * overrunning snprintf's target buffer is *not* an error.
 *
 * 2. For successful writes to streams, the actual number of bytes written
 * to the stream is returned.
 *
 * 3. For successful sprintf/snprintf, the number of bytes that would have
 * been written to an infinite-size buffer (excluding the trailing '\0')
 * is returned.  snprintf will truncate its output to fit in the buffer
 * (ensuring a trailing '\0' unless count == 0), but this is not reflected
 * in the function result.
 *
 * snprintf buffer overrun can be detected by checking for function result
 * greater than or equal to the supplied count.
 */
 
/**************************************************************
 * Original:
 * Patrick Powell Tue Apr 11 09:48:21 PDT 1995
 * A bombproof version of doprnt (dopr) included.
 * Sigh.  This sort of thing is always nasty do deal with.  Note that
 * the version here does not include floating point. (now it does ... tgl)
 **************************************************************/
 
/* Prevent recursion */
#undef  vsnprintf
#undef  snprintf
#undef  vsprintf
#undef  sprintf
#undef  vfprintf
#undef  fprintf
#undef  vprintf
#undef  printf
 
/*
 * Info about where the formatted output is going.
 *
 * dopr and subroutines will not write at/past bufend, but snprintf
 * reserves one byte, ensuring it may place the trailing '\0' there.
 *
 * In snprintf, we use nchars to count the number of bytes dropped on the
 * floor due to buffer overrun.  The correct result of snprintf is thus
 * (bufptr - bufstart) + nchars.  (This isn't as inconsistent as it might
 * seem: nchars is the number of emitted bytes that are not in the buffer now,
 * either because we sent them to the stream or because we couldn't fit them
 * into the buffer to begin with.)
 */
typedef struct
{
    char       *bufptr;         /* next buffer output position */
    char       *bufstart;       /* first buffer element */
    char       *bufend;         /* last+1 buffer element, or NULL */
    /* bufend == NULL is for sprintf, where we assume buf is big enough */
    FILE       *stream;         /* eventual output destination, or NULL */
    int         nchars;         /* # chars sent to stream, or dropped */
    bool        failed;         /* call is a failure; errno is set */
} PrintfTarget;
 
/*
 * Info about the type and value of a formatting parameter.  Note that we
 * don't currently support "long double", "wint_t", or "wchar_t *" data,
 * nor the '%n' formatting code; else we'd need more types.  Also, at this
 * level we need not worry about signed vs unsigned values.
 */
typedef enum
{
    ATYPE_NONE = 0,
    ATYPE_INT,
    ATYPE_LONG,
    ATYPE_LONGLONG,
    ATYPE_DOUBLE,
    ATYPE_CHARPTR
} PrintfArgType;
 
typedef union
{
    int         i;
    long        l;
    long long   ll;
    double      d;
    char       *cptr;
} PrintfArgValue;
 
 
static void flushbuffer(PrintfTarget *target);
static void dopr(PrintfTarget *target, const char *format, va_list args);
 
 
/*
 * Externally visible entry points.
 *
 * All of these are just wrappers around dopr().  Note it's essential that
 * they not change the value of "errno" before reaching dopr().
 */
 
int
pg_vsnprintf(char *str, size_t count, const char *fmt, va_list args)
{
    PrintfTarget target;
    char        onebyte[1];
 
    /*
     * C99 allows the case str == NULL when count == 0.  Rather than
     * special-casing this situation further down, we substitute a one-byte
     * local buffer.  Callers cannot tell, since the function result doesn't
     * depend on count.
     */
    if (count == 0)
    {
        str = onebyte;
        count = 1;
    }
    target.bufstart = target.bufptr = str;
    target.bufend = str + count - 1;
    target.stream = NULL;
    target.nchars = 0;
    target.failed = false;
    dopr(&target, fmt, args);
    *(target.bufptr) = '\0';
    return target.failed ? -1 : (target.bufptr - target.bufstart
                                 + target.nchars);
}
 
int
pg_snprintf(char *str, size_t count, const char *fmt,...)
{
    int         len;
    va_list     args;
 
    va_start(args, fmt);
    len = pg_vsnprintf(str, count, fmt, args);
    va_end(args);
    return len;
}
 
int
pg_vsprintf(char *str, const char *fmt, va_list args)
{
    PrintfTarget target;
 
    target.bufstart = target.bufptr = str;
    target.bufend = NULL;
    target.stream = NULL;
    target.nchars = 0;          /* not really used in this case */
    target.failed = false;
    dopr(&target, fmt, args);
    *(target.bufptr) = '\0';
    return target.failed ? -1 : (target.bufptr - target.bufstart
                                 + target.nchars);
}
 
int
pg_sprintf(char *str, const char *fmt,...)
{
    int         len;
    va_list     args;
 
    va_start(args, fmt);
    len = pg_vsprintf(str, fmt, args);
    va_end(args);
    return len;
}
 
int
pg_vfprintf(FILE *stream, const char *fmt, va_list args)
{
    PrintfTarget target;
    char        buffer[1024];   /* size is arbitrary */
 
    if (stream == NULL)
    {
        errno = EINVAL;
        return -1;
    }
    target.bufstart = target.bufptr = buffer;
    target.bufend = buffer + sizeof(buffer);    /* use the whole buffer */
    target.stream = stream;
    target.nchars = 0;
    target.failed = false;
    dopr(&target, fmt, args);
    /* dump any remaining buffer contents */
    flushbuffer(&target);
    return target.failed ? -1 : target.nchars;
}
 
int
pg_fprintf(FILE *stream, const char *fmt,...)
{
    int         len;
    va_list     args;
 
    va_start(args, fmt);
    len = pg_vfprintf(stream, fmt, args);
    va_end(args);
    return len;
}
 
int
pg_vprintf(const char *fmt, va_list args)
{
    return pg_vfprintf(stdout, fmt, args);
}
 
int
pg_printf(const char *fmt,...)
{
    int         len;
    va_list     args;
 
    va_start(args, fmt);
    len = pg_vfprintf(stdout, fmt, args);
    va_end(args);
    return len;
}
 
/*
 * Attempt to write the entire buffer to target->stream; discard the entire
 * buffer in any case.  Call this only when target->stream is defined.
 */
static void
flushbuffer(PrintfTarget *target)
{
    size_t      nc = target->bufptr - target->bufstart;
 
    /*
     * Don't write anything if we already failed; this is to ensure we
     * preserve the original failure's errno.
     */
    if (!target->failed && nc > 0)
    {
        size_t      written;
 
        written = fwrite(target->bufstart, 1, nc, target->stream);
        target->nchars += written;
        if (written != nc)
            target->failed = true;
    }
    target->bufptr = target->bufstart;
}
 
 
static bool find_arguments(const char *format, va_list args,
                           PrintfArgValue *argvalues);
static void fmtstr(const char *value, int leftjust, int minlen, int maxwidth,
                   int pointflag, PrintfTarget *target);
static void fmtptr(const void *value, PrintfTarget *target);
static void fmtint(long long value, char type, int forcesign,
                   int leftjust, int minlen, int zpad, int precision, int pointflag,
                   PrintfTarget *target);
static void fmtchar(int value, int leftjust, int minlen, PrintfTarget *target);
static void fmtfloat(double value, char type, int forcesign,
                     int leftjust, int minlen, int zpad, int precision, int pointflag,
                     PrintfTarget *target);
static void dostr(const char *str, int slen, PrintfTarget *target);
static void dopr_outch(int c, PrintfTarget *target);
static void dopr_outchmulti(int c, int slen, PrintfTarget *target);
static int  adjust_sign(int is_negative, int forcesign, int *signvalue);
static int  compute_padlen(int minlen, int vallen, int leftjust);
static void leading_pad(int zpad, int signvalue, int *padlen,
                        PrintfTarget *target);
static void trailing_pad(int padlen, PrintfTarget *target);
 
/*
 * If strchrnul exists (it's a glibc-ism, but since adopted by some other
 * platforms), it's a good bit faster than the equivalent manual loop.
 * Use it if possible, and if it doesn't exist, use this replacement.
 *
 * Note: glibc declares this as returning "char *", but that would require
 * casting away const internally, so we don't follow that detail.
 *
 * Note: macOS has this too as of Sequoia 15.4, but it's hidden behind
 * a deployment-target check that causes compile errors if the deployment
 * target isn't high enough.  So !HAVE_DECL_STRCHRNUL may mean "yes it's
 * declared, but it doesn't compile".  To avoid failing in that scenario,
 * use a macro to avoid matching <string.h>'s name.
 */
#if !HAVE_DECL_STRCHRNUL
 
#define strchrnul pg_strchrnul
 
static inline const char *
strchrnul(const char *s, int c)
{
    while (*s != '\0' && *s != c)
        s++;
    return s;
}
 
#endif                          /* !HAVE_DECL_STRCHRNUL */
 
 
/*
 * dopr(): the guts of *printf for all cases.
 */
static void
dopr(PrintfTarget *target, const char *format, va_list args)
{
    int         save_errno = errno;
    const char *first_pct = NULL;
    int         ch;
    bool        have_dollar;
    bool        have_star;
    bool        afterstar;
    int         accum;
    int         longlongflag;
    int         longflag;
    int         pointflag;
    int         leftjust;
    int         fieldwidth;
    int         precision;
    int         zpad;
    int         forcesign;
    int         fmtpos;
    int         cvalue;
    long long   numvalue;
    double      fvalue;
    const char *strvalue;
    PrintfArgValue argvalues[PG_NL_ARGMAX + 1];
 
    /*
     * Initially, we suppose the format string does not use %n$.  The first
     * time we come to a conversion spec that has that, we'll call
     * find_arguments() to check for consistent use of %n$ and fill the
     * argvalues array with the argument values in the correct order.
     */
    have_dollar = false;
 
    while (*format != '\0')
    {
        /* Locate next conversion specifier */
        if (*format != '%')
        {
            /* Scan to next '%' or end of string */
            const char *next_pct = strchrnul(format + 1, '%');
 
            /* Dump literal data we just scanned over */
            dostr(format, next_pct - format, target);
            if (target->failed)
                break;
 
            if (*next_pct == '\0')
                break;
            format = next_pct;
        }
 
        /*
         * Remember start of first conversion spec; if we find %n$, then it's
         * sufficient for find_arguments() to start here, without rescanning
         * earlier literal text.
         */
        if (first_pct == NULL)
            first_pct = format;
 
        /* Process conversion spec starting at *format */
        format++;
 
        /* Fast path for conversion spec that is exactly %s */
        if (*format == 's')
        {
            format++;
            strvalue = va_arg(args, char *);
            if (strvalue == NULL)
                strvalue = "(null)";
            dostr(strvalue, strlen(strvalue), target);
            if (target->failed)
                break;
            continue;
        }
 
        fieldwidth = precision = zpad = leftjust = forcesign = 0;
        longflag = longlongflag = pointflag = 0;
        fmtpos = accum = 0;
        have_star = afterstar = false;
nextch2:
        ch = *format++;
        switch (ch)
        {
            case '-':
                leftjust = 1;
                goto nextch2;
            case '+':
                forcesign = 1;
                goto nextch2;
            case '0':
                /* set zero padding if no nonzero digits yet */
                if (accum == 0 && !pointflag)
                    zpad = '0';
                /* FALL THRU */
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
                accum = accum * 10 + (ch - '0');
                goto nextch2;
            case '.':
                if (have_star)
                    have_star = false;
                else
                    fieldwidth = accum;
                pointflag = 1;
                accum = 0;
                goto nextch2;
            case '*':
                if (have_dollar)
                {
                    /*
                     * We'll process value after reading n$.  Note it's OK to
                     * assume have_dollar is set correctly, because in a valid
                     * format string the initial % must have had n$ if * does.
                     */
                    afterstar = true;
                }
                else
                {
                    /* fetch and process value now */
                    int         starval = va_arg(args, int);
 
                    if (pointflag)
                    {
                        precision = starval;
                        if (precision < 0)
                        {
                            precision = 0;
                            pointflag = 0;
                        }
                    }
                    else
                    {
                        fieldwidth = starval;
                        if (fieldwidth < 0)
                        {
                            leftjust = 1;
                            fieldwidth = -fieldwidth;
                        }
                    }
                }
                have_star = true;
                accum = 0;
                goto nextch2;
            case '$':
                /* First dollar sign? */
                if (!have_dollar)
                {
                    /* Yup, so examine all conversion specs in format */
                    if (!find_arguments(first_pct, args, argvalues))
                        goto bad_format;
                    have_dollar = true;
                }
                if (afterstar)
                {
                    /* fetch and process star value */
                    int         starval = argvalues[accum].i;
 
                    if (pointflag)
                    {
                        precision = starval;
                        if (precision < 0)
                        {
                            precision = 0;
                            pointflag = 0;
                        }
                    }
                    else
                    {
                        fieldwidth = starval;
                        if (fieldwidth < 0)
                        {
                            leftjust = 1;
                            fieldwidth = -fieldwidth;
                        }
                    }
                    afterstar = false;
                }
                else
                    fmtpos = accum;
                accum = 0;
                goto nextch2;
            case 'l':
                if (longflag)
                    longlongflag = 1;
                else
                    longflag = 1;
                goto nextch2;
            case 'z':
#if SIZEOF_SIZE_T == SIZEOF_LONG
                longflag = 1;
#elif SIZEOF_SIZE_T == SIZEOF_LONG_LONG
                longlongflag = 1;
#else
#error "cannot find integer type of the same size as size_t"
#endif
                goto nextch2;
            case 'h':
            case '\'':
                /* ignore these */
                goto nextch2;
            case 'd':
            case 'i':
                if (!have_star)
                {
                    if (pointflag)
                        precision = accum;
                    else
                        fieldwidth = accum;
                }
                if (have_dollar)
                {
                    if (longlongflag)
                        numvalue = argvalues[fmtpos].ll;
                    else if (longflag)
                        numvalue = argvalues[fmtpos].l;
                    else
                        numvalue = argvalues[fmtpos].i;
                }
                else
                {
                    if (longlongflag)
                        numvalue = va_arg(args, long long);
                    else if (longflag)
                        numvalue = va_arg(args, long);
                    else
                        numvalue = va_arg(args, int);
                }
                fmtint(numvalue, ch, forcesign, leftjust, fieldwidth, zpad,
                       precision, pointflag, target);
                break;
            case 'o':
            case 'u':
            case 'x':
            case 'X':
                if (!have_star)
                {
                    if (pointflag)
                        precision = accum;
                    else
                        fieldwidth = accum;
                }
                if (have_dollar)
                {
                    if (longlongflag)
                        numvalue = (unsigned long long) argvalues[fmtpos].ll;
                    else if (longflag)
                        numvalue = (unsigned long) argvalues[fmtpos].l;
                    else
                        numvalue = (unsigned int) argvalues[fmtpos].i;
                }
                else
                {
                    if (longlongflag)
                        numvalue = (unsigned long long) va_arg(args, long long);
                    else if (longflag)
                        numvalue = (unsigned long) va_arg(args, long);
                    else
                        numvalue = (unsigned int) va_arg(args, int);
                }
                fmtint(numvalue, ch, forcesign, leftjust, fieldwidth, zpad,
                       precision, pointflag, target);
                break;
            case 'c':
                if (!have_star)
                {
                    if (pointflag)
                        precision = accum;
                    else
                        fieldwidth = accum;
                }
                if (have_dollar)
                    cvalue = (unsigned char) argvalues[fmtpos].i;
                else
                    cvalue = (unsigned char) va_arg(args, int);
                fmtchar(cvalue, leftjust, fieldwidth, target);
                break;
            case 's':
                if (!have_star)
                {
                    if (pointflag)
                        precision = accum;
                    else
                        fieldwidth = accum;
                }
                if (have_dollar)
                    strvalue = argvalues[fmtpos].cptr;
                else
                    strvalue = va_arg(args, char *);
                /* If string is NULL, silently substitute "(null)" */
                if (strvalue == NULL)
                    strvalue = "(null)";
                fmtstr(strvalue, leftjust, fieldwidth, precision, pointflag,
                       target);
                break;
            case 'p':
                /* fieldwidth/leftjust are ignored ... */
                if (have_dollar)
                    strvalue = argvalues[fmtpos].cptr;
                else
                    strvalue = va_arg(args, char *);
                fmtptr((const void *) strvalue, target);
                break;
            case 'e':
            case 'E':
            case 'f':
            case 'g':
            case 'G':
                if (!have_star)
                {
                    if (pointflag)
                        precision = accum;
                    else
                        fieldwidth = accum;
                }
                if (have_dollar)
                    fvalue = argvalues[fmtpos].d;
                else
                    fvalue = va_arg(args, double);
                fmtfloat(fvalue, ch, forcesign, leftjust,
                         fieldwidth, zpad,
                         precision, pointflag,
                         target);
                break;
            case 'm':
                {
                    char        errbuf[PG_STRERROR_R_BUFLEN];
                    const char *errm = strerror_r(save_errno,
                                                  errbuf, sizeof(errbuf));
 
                    dostr(errm, strlen(errm), target);
                }
                break;
            case '%':
                dopr_outch('%', target);
                break;
            default:
 
                /*
                 * Anything else --- in particular, '\0' indicating end of
                 * format string --- is bogus.
                 */
                goto bad_format;
        }
 
        /* Check for failure after each conversion spec */
        if (target->failed)
            break;
    }
 
    return;
 
bad_format:
    errno = EINVAL;
    target->failed = true;
}
 
/*
 * find_arguments(): sort out the arguments for a format spec with %n$
 *
 * If format is valid, return true and fill argvalues[i] with the value
 * for the conversion spec that has %i$ or *i$.  Else return false.
 */
static bool
find_arguments(const char *format, va_list args,
               PrintfArgValue *argvalues)
{
    int         ch;
    bool        afterstar;
    int         accum;
    int         longlongflag;
    int         longflag;
    int         fmtpos;
    int         i;
    int         last_dollar = 0;    /* Init to "no dollar arguments known" */
    PrintfArgType argtypes[PG_NL_ARGMAX + 1] = {0};
 
    /*
     * This loop must accept the same format strings as the one in dopr().
     * However, we don't need to analyze them to the same level of detail.
     *
     * Since we're only called if there's a dollar-type spec somewhere, we can
     * fail immediately if we find a non-dollar spec.  Per the C99 standard,
     * all argument references in the format string must be one or the other.
     */
    while (*format != '\0')
    {
        /* Locate next conversion specifier */
        if (*format != '%')
        {
            /* Unlike dopr, we can just quit if there's no more specifiers */
            format = strchr(format + 1, '%');
            if (format == NULL)
                break;
        }
 
        /* Process conversion spec starting at *format */
        format++;
        longflag = longlongflag = 0;
        fmtpos = accum = 0;
        afterstar = false;
nextch1:
        ch = *format++;
        switch (ch)
        {
            case '-':
            case '+':
                goto nextch1;
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
                accum = accum * 10 + (ch - '0');
                goto nextch1;
            case '.':
                accum = 0;
                goto nextch1;
            case '*':
                if (afterstar)
                    return false;   /* previous star missing dollar */
                afterstar = true;
                accum = 0;
                goto nextch1;
            case '$':
                if (accum <= 0 || accum > PG_NL_ARGMAX)
                    return false;
                if (afterstar)
                {
                    if (argtypes[accum] &&
                        argtypes[accum] != ATYPE_INT)
                        return false;
                    argtypes[accum] = ATYPE_INT;
                    last_dollar = Max(last_dollar, accum);
                    afterstar = false;
                }
                else
                    fmtpos = accum;
                accum = 0;
                goto nextch1;
            case 'l':
                if (longflag)
                    longlongflag = 1;
                else
                    longflag = 1;
                goto nextch1;
            case 'z':
#if SIZEOF_SIZE_T == SIZEOF_LONG
                longflag = 1;
#elif SIZEOF_SIZE_T == SIZEOF_LONG_LONG
                longlongflag = 1;
#else
#error "cannot find integer type of the same size as size_t"
#endif
                goto nextch1;
            case 'h':
            case '\'':
                /* ignore these */
                goto nextch1;
            case 'd':
            case 'i':
            case 'o':
            case 'u':
            case 'x':
            case 'X':
                if (fmtpos)
                {
                    PrintfArgType atype;
 
                    if (longlongflag)
                        atype = ATYPE_LONGLONG;
                    else if (longflag)
                        atype = ATYPE_LONG;
                    else
                        atype = ATYPE_INT;
                    if (argtypes[fmtpos] &&
                        argtypes[fmtpos] != atype)
                        return false;
                    argtypes[fmtpos] = atype;
                    last_dollar = Max(last_dollar, fmtpos);
                }
                else
                    return false;   /* non-dollar conversion spec */
                break;
            case 'c':
                if (fmtpos)
                {
                    if (argtypes[fmtpos] &&
                        argtypes[fmtpos] != ATYPE_INT)
                        return false;
                    argtypes[fmtpos] = ATYPE_INT;
                    last_dollar = Max(last_dollar, fmtpos);
                }
                else
                    return false;   /* non-dollar conversion spec */
                break;
            case 's':
            case 'p':
                if (fmtpos)
                {
                    if (argtypes[fmtpos] &&
                        argtypes[fmtpos] != ATYPE_CHARPTR)
                        return false;
                    argtypes[fmtpos] = ATYPE_CHARPTR;
                    last_dollar = Max(last_dollar, fmtpos);
                }
                else
                    return false;   /* non-dollar conversion spec */
                break;
            case 'e':
            case 'E':
            case 'f':
            case 'g':
            case 'G':
                if (fmtpos)
                {
                    if (argtypes[fmtpos] &&
                        argtypes[fmtpos] != ATYPE_DOUBLE)
                        return false;
                    argtypes[fmtpos] = ATYPE_DOUBLE;
                    last_dollar = Max(last_dollar, fmtpos);
                }
                else
                    return false;   /* non-dollar conversion spec */
                break;
            case 'm':
            case '%':
                break;
            default:
                return false;   /* bogus format string */
        }
 
        /*
         * If we finish the spec with afterstar still set, there's a
         * non-dollar star in there.
         */
        if (afterstar)
            return false;       /* non-dollar conversion spec */
    }
 
    /*
     * Format appears valid so far, so collect the arguments in physical
     * order.  (Since we rejected any non-dollar specs that would have
     * collected arguments, we know that dopr() hasn't collected any yet.)
     */
    for (i = 1; i <= last_dollar; i++)
    {
        switch (argtypes[i])
        {
            case ATYPE_NONE:
                return false;
            case ATYPE_INT:
                argvalues[i].i = va_arg(args, int);
                break;
            case ATYPE_LONG:
                argvalues[i].l = va_arg(args, long);
                break;
            case ATYPE_LONGLONG:
                argvalues[i].ll = va_arg(args, long long);
                break;
            case ATYPE_DOUBLE:
                argvalues[i].d = va_arg(args, double);
                break;
            case ATYPE_CHARPTR:
                argvalues[i].cptr = va_arg(args, char *);
                break;
        }
    }
 
    return true;
}
 
static void
fmtstr(const char *value, int leftjust, int minlen, int maxwidth,
       int pointflag, PrintfTarget *target)
{
    int         padlen,
                vallen;         /* amount to pad */
 
    /*
     * If a maxwidth (precision) is specified, we must not fetch more bytes
     * than that.
     */
    if (pointflag)
        vallen = strnlen(value, maxwidth);
    else
        vallen = strlen(value);
 
    padlen = compute_padlen(minlen, vallen, leftjust);
 
    if (padlen > 0)
    {
        dopr_outchmulti(' ', padlen, target);
        padlen = 0;
    }
 
    dostr(value, vallen, target);
 
    trailing_pad(padlen, target);
}
 
static void
fmtptr(const void *value, PrintfTarget *target)
{
    int         vallen;
    char        convert[64];
 
    /* we rely on regular C library's snprintf to do the basic conversion */
    vallen = snprintf(convert, sizeof(convert), "%p", value);
    if (vallen < 0)
        target->failed = true;
    else
        dostr(convert, vallen, target);
}
 
static void
fmtint(long long value, char type, int forcesign, int leftjust,
       int minlen, int zpad, int precision, int pointflag,
       PrintfTarget *target)
{
    unsigned long long uvalue;
    int         base;
    int         dosign;
    const char *cvt = "0123456789abcdef";
    int         signvalue = 0;
    char        convert[64];
    int         vallen = 0;
    int         padlen;         /* amount to pad */
    int         zeropad;        /* extra leading zeroes */
 
    switch (type)
    {
        case 'd':
        case 'i':
            base = 10;
            dosign = 1;
            break;
        case 'o':
            base = 8;
            dosign = 0;
            break;
        case 'u':
            base = 10;
            dosign = 0;
            break;
        case 'x':
            base = 16;
            dosign = 0;
            break;
        case 'X':
            cvt = "0123456789ABCDEF";
            base = 16;
            dosign = 0;
            break;
        default:
            return;             /* keep compiler quiet */
    }
 
    /* disable MSVC warning about applying unary minus to an unsigned value */
#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4146)
#endif
    /* Handle +/- */
    if (dosign && adjust_sign((value < 0), forcesign, &signvalue))
        uvalue = -(unsigned long long) value;
    else
        uvalue = (unsigned long long) value;
#ifdef _MSC_VER
#pragma warning(pop)
#endif
 
    /*
     * SUS: the result of converting 0 with an explicit precision of 0 is no
     * characters
     */
    if (value == 0 && pointflag && precision == 0)
        vallen = 0;
    else
    {
        /*
         * Convert integer to string.  We special-case each of the possible
         * base values so as to avoid general-purpose divisions.  On most
         * machines, division by a fixed constant can be done much more
         * cheaply than a general divide.
         */
        if (base == 10)
        {
            do
            {
                convert[sizeof(convert) - (++vallen)] = cvt[uvalue % 10];
                uvalue = uvalue / 10;
            } while (uvalue);
        }
        else if (base == 16)
        {
            do
            {
                convert[sizeof(convert) - (++vallen)] = cvt[uvalue % 16];
                uvalue = uvalue / 16;
            } while (uvalue);
        }
        else                    /* base == 8 */
        {
            do
            {
                convert[sizeof(convert) - (++vallen)] = cvt[uvalue % 8];
                uvalue = uvalue / 8;
            } while (uvalue);
        }
    }
 
    zeropad = Max(0, precision - vallen);
 
    padlen = compute_padlen(minlen, vallen + zeropad, leftjust);
 
    leading_pad(zpad, signvalue, &padlen, target);
 
    if (zeropad > 0)
        dopr_outchmulti('0', zeropad, target);
 
    dostr(convert + sizeof(convert) - vallen, vallen, target);
 
    trailing_pad(padlen, target);
}
 
static void
fmtchar(int value, int leftjust, int minlen, PrintfTarget *target)
{
    int         padlen;         /* amount to pad */
 
    padlen = compute_padlen(minlen, 1, leftjust);
 
    if (padlen > 0)
    {
        dopr_outchmulti(' ', padlen, target);
        padlen = 0;
    }
 
    dopr_outch(value, target);
 
    trailing_pad(padlen, target);
}
 
static void
fmtfloat(double value, char type, int forcesign, int leftjust,
         int minlen, int zpad, int precision, int pointflag,
         PrintfTarget *target)
{
    int         signvalue = 0;
    int         prec;
    int         vallen;
    char        fmt[8];
    char        convert[1024];
    int         zeropadlen = 0; /* amount to pad with zeroes */
    int         padlen;         /* amount to pad with spaces */
 
    /*
     * We rely on the regular C library's snprintf to do the basic conversion,
     * then handle padding considerations here.
     *
     * The dynamic range of "double" is about 1E+-308 for IEEE math, and not
     * too wildly more than that with other hardware.  In "f" format, snprintf
     * could therefore generate at most 308 characters to the left of the
     * decimal point; while we need to allow the precision to get as high as
     * 308+17 to ensure that we don't truncate significant digits from very
     * small values.  To handle both these extremes, we use a buffer of 1024
     * bytes and limit requested precision to 350 digits; this should prevent
     * buffer overrun even with non-IEEE math.  If the original precision
     * request was more than 350, separately pad with zeroes.
     *
     * We handle infinities and NaNs specially to ensure platform-independent
     * output.
     */
    if (precision < 0)          /* cover possible overflow of "accum" */
        precision = 0;
    prec = Min(precision, 350);
 
    if (isnan(value))
    {
        strcpy(convert, "NaN");
        vallen = 3;
        /* no zero padding, regardless of precision spec */
    }
    else
    {
        /*
         * Handle sign (NaNs have no sign, so we don't do this in the case
         * above).  "value < 0.0" will not be true for IEEE minus zero, so we
         * detect that by looking for the case where value equals 0.0
         * according to == but not according to memcmp.
         */
        static const double dzero = 0.0;
 
        if (adjust_sign((value < 0.0 ||
                         (value == 0.0 &&
                          memcmp(&value, &dzero, sizeof(double)) != 0)),
                        forcesign, &signvalue))
            value = -value;
 
        if (isinf(value))
        {
            strcpy(convert, "Infinity");
            vallen = 8;
            /* no zero padding, regardless of precision spec */
        }
        else if (pointflag)
        {
            zeropadlen = precision - prec;
            fmt[0] = '%';
            fmt[1] = '.';
            fmt[2] = '*';
            fmt[3] = type;
            fmt[4] = '\0';
            vallen = snprintf(convert, sizeof(convert), fmt, prec, value);
        }
        else
        {
            fmt[0] = '%';
            fmt[1] = type;
            fmt[2] = '\0';
            vallen = snprintf(convert, sizeof(convert), fmt, value);
        }
        if (vallen < 0)
            goto fail;
    }
 
    padlen = compute_padlen(minlen, vallen + zeropadlen, leftjust);
 
    leading_pad(zpad, signvalue, &padlen, target);
 
    if (zeropadlen > 0)
    {
        /* If 'e' or 'E' format, inject zeroes before the exponent */
        char       *epos = strrchr(convert, 'e');
 
        if (!epos)
            epos = strrchr(convert, 'E');
        if (epos)
        {
            /* pad before exponent */
            dostr(convert, epos - convert, target);
            dopr_outchmulti('0', zeropadlen, target);
            dostr(epos, vallen - (epos - convert), target);
        }
        else
        {
            /* no exponent, pad after the digits */
            dostr(convert, vallen, target);
            dopr_outchmulti('0', zeropadlen, target);
        }
    }
    else
    {
        /* no zero padding, just emit the number as-is */
        dostr(convert, vallen, target);
    }
 
    trailing_pad(padlen, target);
    return;
 
fail:
    target->failed = true;
}
 
/*
 * Nonstandard entry point to print a double value efficiently.
 *
 * This is approximately equivalent to strfromd(), but has an API more
 * adapted to what float8out() wants.  The behavior is like snprintf()
 * with a format of "%.ng", where n is the specified precision.
 * However, the target buffer must be nonempty (i.e. count > 0), and
 * the precision is silently bounded to a sane range.
 */
int
pg_strfromd(char *str, size_t count, int precision, double value)
{
    PrintfTarget target;
    int         signvalue = 0;
    int         vallen;
    char        fmt[8];
    char        convert[64];
 
    /* Set up the target like pg_snprintf, but require nonempty buffer */
    Assert(count > 0);
    target.bufstart = target.bufptr = str;
    target.bufend = str + count - 1;
    target.stream = NULL;
    target.nchars = 0;
    target.failed = false;
 
    /*
     * We bound precision to a reasonable range; the combination of this and
     * the knowledge that we're using "g" format without padding allows the
     * convert[] buffer to be reasonably small.
     */
    if (precision < 1)
        precision = 1;
    else if (precision > 32)
        precision = 32;
 
    /*
     * The rest is just an inlined version of the fmtfloat() logic above,
     * simplified using the knowledge that no padding is wanted.
     */
    if (isnan(value))
    {
        strcpy(convert, "NaN");
        vallen = 3;
    }
    else
    {
        static const double dzero = 0.0;
 
        if (value < 0.0 ||
            (value == 0.0 &&
             memcmp(&value, &dzero, sizeof(double)) != 0))
        {
            signvalue = '-';
            value = -value;
        }
 
        if (isinf(value))
        {
            strcpy(convert, "Infinity");
            vallen = 8;
        }
        else
        {
            fmt[0] = '%';
            fmt[1] = '.';
            fmt[2] = '*';
            fmt[3] = 'g';
            fmt[4] = '\0';
            vallen = snprintf(convert, sizeof(convert), fmt, precision, value);
            if (vallen < 0)
            {
                target.failed = true;
                goto fail;
            }
        }
    }
 
    if (signvalue)
        dopr_outch(signvalue, &target);
 
    dostr(convert, vallen, &target);
 
fail:
    *(target.bufptr) = '\0';
    return target.failed ? -1 : (target.bufptr - target.bufstart
                                 + target.nchars);
}
 
 
static void
dostr(const char *str, int slen, PrintfTarget *target)
{
    /* fast path for common case of slen == 1 */
    if (slen == 1)
    {
        dopr_outch(*str, target);
        return;
    }
 
    while (slen > 0)
    {
        int         avail;
 
        if (target->bufend != NULL)
            avail = target->bufend - target->bufptr;
        else
            avail = slen;
        if (avail <= 0)
        {
            /* buffer full, can we dump to stream? */
            if (target->stream == NULL)
            {
                target->nchars += slen; /* no, lose the data */
                return;
            }
            flushbuffer(target);
            continue;
        }
        avail = Min(avail, slen);
        memmove(target->bufptr, str, avail);
        target->bufptr += avail;
        str += avail;
        slen -= avail;
    }
}
 
static void
dopr_outch(int c, PrintfTarget *target)
{
    if (target->bufend != NULL && target->bufptr >= target->bufend)
    {
        /* buffer full, can we dump to stream? */
        if (target->stream == NULL)
        {
            target->nchars++;   /* no, lose the data */
            return;
        }
        flushbuffer(target);
    }
    *(target->bufptr++) = c;
}
 
static void
dopr_outchmulti(int c, int slen, PrintfTarget *target)
{
    /* fast path for common case of slen == 1 */
    if (slen == 1)
    {
        dopr_outch(c, target);
        return;
    }
 
    while (slen > 0)
    {
        int         avail;
 
        if (target->bufend != NULL)
            avail = target->bufend - target->bufptr;
        else
            avail = slen;
        if (avail <= 0)
        {
            /* buffer full, can we dump to stream? */
            if (target->stream == NULL)
            {
                target->nchars += slen; /* no, lose the data */
                return;
            }
            flushbuffer(target);
            continue;
        }
        avail = Min(avail, slen);
        memset(target->bufptr, c, avail);
        target->bufptr += avail;
        slen -= avail;
    }
}
 
 
static int
adjust_sign(int is_negative, int forcesign, int *signvalue)
{
    if (is_negative)
    {
        *signvalue = '-';
        return true;
    }
    else if (forcesign)
        *signvalue = '+';
    return false;
}
 
 
static int
compute_padlen(int minlen, int vallen, int leftjust)
{
    int         padlen;
 
    padlen = minlen - vallen;
    if (padlen < 0)
        padlen = 0;
    if (leftjust)
        padlen = -padlen;
    return padlen;
}
 
 
static void
leading_pad(int zpad, int signvalue, int *padlen, PrintfTarget *target)
{
    int         maxpad;
 
    if (*padlen > 0 && zpad)
    {
        if (signvalue)
        {
            dopr_outch(signvalue, target);
            --(*padlen);
            signvalue = 0;
        }
        if (*padlen > 0)
        {
            dopr_outchmulti(zpad, *padlen, target);
            *padlen = 0;
        }
    }
    maxpad = (signvalue != 0);
    if (*padlen > maxpad)
    {
        dopr_outchmulti(' ', *padlen - maxpad, target);
        *padlen = maxpad;
    }
    if (signvalue)
    {
        dopr_outch(signvalue, target);
        if (*padlen > 0)
            --(*padlen);
        else if (*padlen < 0)
            ++(*padlen);
    }
}
 
 
static void
trailing_pad(int padlen, PrintfTarget *target)
{
    if (padlen < 0)
        dopr_outchmulti(' ', -padlen, target);
}