vstring.c

[詳解]

/*++
/* NAME
/*  vstring 3
/* SUMMARY
/*  arbitrary-length string manager
/* SYNOPSIS
/*  #include <vstring.h>
/*
/*  VSTRING *vstring_alloc(len)
/*  ssize_t len;
/*
/*  vstring_ctl(vp, type, value, ..., VSTRING_CTL_END)
/*  VSTRING *vp;
/*  int type;
/*
/*  VSTRING *vstring_free(vp)
/*  VSTRING *vp;
/*
/*  char    *vstring_str(vp)
/*  VSTRING *vp;
/*
/*  ssize_t VSTRING_LEN(vp)
/*  VSTRING *vp;
/*
/*  char    *vstring_end(vp)
/*  VSTRING *vp;
/*
/*  void    VSTRING_ADDCH(vp, ch)
/*  VSTRING *vp;
/*  int ch;
/*
/*  int VSTRING_SPACE(vp, len)
/*  VSTRING *vp;
/*  ssize_t len;
/*
/*  ssize_t vstring_avail(vp)
/*  VSTRING *vp;
/*
/*  VSTRING *vstring_truncate(vp, len)
/*  VSTRING *vp;
/*  ssize_t len;
/*
/*  void    VSTRING_RESET(vp)
/*  VSTRING *vp;
/*
/*  void    VSTRING_TERMINATE(vp)
/*  VSTRING *vp;
/*
/*  void    VSTRING_SKIP(vp)
/*  VSTRING *vp;
/*
/*  VSTRING *vstring_strcpy(vp, src)
/*  VSTRING *vp;
/*  const char *src;
/*
/*  VSTRING *vstring_strncpy(vp, src, len)
/*  VSTRING *vp;
/*  const char *src;
/*  ssize_t len;
/*
/*  VSTRING *vstring_strcat(vp, src)
/*  VSTRING *vp;
/*  const char *src;
/*
/*  VSTRING *vstring_strncat(vp, src, len)
/*  VSTRING *vp;
/*  const char *src;
/*  ssize_t len;
/*
/*  VSTRING *vstring_memcpy(vp, src, len)
/*  VSTRING *vp;
/*  const char *src;
/*  ssize_t len;
/*
/*  VSTRING *vstring_memcat(vp, src, len)
/*  VSTRING *vp;
/*  const char *src;
/*  ssize_t len;
/*
/*  char    *vstring_memchr(vp, ch)
/*  VSTRING *vp;
/*  int ch;
/*
/*  VSTRING *vstring_insert(vp, start, src, len)
/*  VSTRING *vp;
/*  ssize_t start;
/*  const char *src;
/*  ssize_t len;
/*
/*  VSTRING *vstring_prepend(vp, src, len)
/*  VSTRING *vp;
/*  const char *src;
/*  ssize_t len;
/*
/*  VSTRING *vstring_sprintf(vp, format, ...)
/*  VSTRING *vp;
/*  const char *format;
/*
/*  VSTRING *vstring_sprintf_append(vp, format, ...)
/*  VSTRING *vp;
/*  const char *format;
/*
/*  VSTRING *vstring_sprintf_prepend(vp, format, ...)
/*  VSTRING *vp;
/*  const char *format;
/*
/*  VSTRING *vstring_vsprintf(vp, format, ap)
/*  VSTRING *vp;
/*  const char *format;
/*  va_list ap;
/*
/*  VSTRING *vstring_vsprintf_append(vp, format, ap)
/*  VSTRING *vp;
/*  const char *format;
/*  va_list ap;
/* AUXILIARY FUNCTIONS
/*  char    *vstring_export(vp)
/*  VSTRING *vp;
/*
/*  VSTRING *vstring_import(str)
/*  char    *str;
/* DESCRIPTION
/*  The functions and macros in this module implement arbitrary-length
/*  strings and common operations on those strings. The strings do not
/*  need to be null terminated and may contain arbitrary binary data.
/*  The strings manage their own memory and grow automatically when full.
/*  The optional string null terminator does not add to the string length.
/*
/*  vstring_alloc() allocates storage for a variable-length string
/*  of at least "len" bytes. The minimal length is 1. The result
/*  is a null-terminated string of length zero.
/*
/*  vstring_ctl() gives additional control over VSTRING behavior.
/*  The function takes a VSTRING pointer and a list of zero or
/*  more macros with zer or more arguments, terminated with
/*  CA_VSTRING_CTL_END which has none.
/* .IP "CA_VSTRING_CTL_MAXLEN(ssize_t len)"
/*  Specifies a hard upper limit on a string's length. When the
/*  length would be exceeded, the program simulates a memory
/*  allocation problem (i.e. it terminates through msg_fatal()).
/*  This fuctionality is currently unimplemented.
/* .IP "CA_VSTRING_CTL_EXACT (no argument)"
/*  Allocate the requested amounts, instead of rounding up.
/*  This should be used for tests only.
/* .IP "CA_VSTRING_CTL_END (no argument)"
/*  Specifies the end of the argument list. Forgetting to terminate
/*  the argument list may cause the program to crash.
/* .PP
/*  VSTRING_SPACE() ensures that the named string has room for
/*  "len" more characters. VSTRING_SPACE() is an unsafe macro
/*  that either returns zero or never returns.
/*
/*  vstring_avail() returns the number of bytes that can be placed
/*  into the buffer before the buffer would need to grow.
/*
/*  vstring_free() reclaims storage for a variable-length string.
/*  It conveniently returns a null pointer.
/*
/*  vstring_str() is a macro that returns the string value
/*  of a variable-length string. It is a safe macro that
/*  evaluates its argument only once.
/*
/*  VSTRING_LEN() is a macro that returns the current length of
/*  its argument (i.e. the distance from the start of the string
/*  to the current write position). VSTRING_LEN() is an unsafe macro
/*  that evaluates its argument more than once.
/*
/*  vstring_end() is a macro that returns the current write position of
/*  its argument. It is a safe macro that evaluates its argument only once.
/*
/*  VSTRING_ADDCH() adds a character to a variable-length string
/*  and extends the string if it fills up.  \fIvs\fP is a pointer
/*  to a VSTRING structure; \fIch\fP the character value to be written.
/*  The result is the written character.
/*  Note that VSTRING_ADDCH() is an unsafe macro that evaluates some
/*  arguments more than once. The result is NOT null-terminated.
/*
/*  vstring_truncate() truncates the named string to the specified
/*  length. If length is negative, the trailing portion is kept.
/*  The operation has no effect when the string is shorter.
/*  The string is not null-terminated.
/*
/*  VSTRING_RESET() is a macro that resets the write position of its
/*  string argument to the very beginning. Note that VSTRING_RESET()
/*  is an unsafe macro that evaluates some arguments more than once.
/*  The result is NOT null-terminated.
/*
/*  VSTRING_TERMINATE() null-terminates its string argument.
/*  VSTRING_TERMINATE() is an unsafe macro that evaluates some
/*  arguments more than once.
/*  VSTRING_TERMINATE() does not return an interesting result.
/*
/*  VSTRING_SKIP() is a macro that moves the write position to the first
/*  null byte after the current write position. VSTRING_SKIP() is an unsafe
/*  macro that evaluates some arguments more than once.
/*
/*  vstring_strcpy() copies a null-terminated string to a variable-length
/*  string. \fIsrc\fP provides the data to be copied; \fIvp\fP is the
/*  target and result value.  The result is null-terminated.
/*
/*  vstring_strncpy() copies at most \fIlen\fR characters. Otherwise it is
/*  identical to vstring_strcpy().
/*
/*  vstring_strcat() appends a null-terminated string to a variable-length
/*  string. \fIsrc\fP provides the data to be copied; \fIvp\fP is the
/*  target and result value.  The result is null-terminated.
/*
/*  vstring_strncat() copies at most \fIlen\fR characters. Otherwise it is
/*  identical to vstring_strcat().
/*
/*  vstring_memcpy() copies \fIlen\fR bytes to a variable-length string.
/*  \fIsrc\fP provides the data to be copied; \fIvp\fP is the
/*  target and result value.  The result is not null-terminated.
/*
/*  vstring_memcat() appends \fIlen\fR bytes to a variable-length string.
/*  \fIsrc\fP provides the data to be copied; \fIvp\fP is the
/*  target and result value.  The result is not null-terminated.
/*
/*  vstring_memchr() locates a byte in a variable-length string.
/*
/*  vstring_insert() inserts a buffer content into a variable-length
/*  string at the specified start position. The result is
/*  null-terminated.
/*
/*  vstring_prepend() prepends a buffer content to a variable-length
/*  string. The result is null-terminated.
/*
/*  vstring_sprintf() produces a formatted string according to its
/*  \fIformat\fR argument. See vstring_vsprintf() for details.
/*
/*  vstring_sprintf_append() is like vstring_sprintf(), but appends
/*  to the end of the result buffer.
/*
/*  vstring_sprintf_append() is like vstring_sprintf(), but prepends
/*  to the beginning of the result buffer.
/*
/*  vstring_vsprintf() returns a null-terminated string according to
/*  the \fIformat\fR argument. It understands the s, c, d, u,
/*  o, x, X, p, e, f and g format types, the l modifier, field width
/*  and precision, sign, and null or space padding. This module
/*  can format strings as large as available memory permits.
/*
/*  vstring_vsprintf_append() is like vstring_vsprintf(), but appends
/*  to the end of the result buffer.
/*
/*  In addition to stdio-like format specifiers, vstring_vsprintf()
/*  recognizes %m and expands it to the corresponding errno text.
/*
/*  vstring_export() extracts the string value from a VSTRING.
/*  The VSTRING is destroyed. The result should be passed to myfree().
/*
/*  vstring_import() takes a `bare' string and converts it to
/*  a VSTRING. The string argument must be obtained from mymalloc().
/*  The string argument is not copied.
/* DIAGNOSTICS
/*  Fatal errors: memory allocation failure.
/* BUGS
/*  Auto-resizing may change the address of the string data in
/*  a vstring structure. Beware of dangling pointers.
/* HISTORY
/* .ad
/* .fi
/*  A vstring module appears in the UNPROTO software by Wietse Venema.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*
/*  Wietse Venema
/*  Google, Inc.
/*  111 8th Avenue
/*  New York, NY 10011, USA
/*--*/

/* System libraries. */

#include <sys_defs.h>
#include <stddef.h>
#include <stdlib.h>         /* 44BSD stdarg.h uses abort() */
#include <stdarg.h>
#include <string.h>

/* Utility library. */

#include "mymalloc.h"
#include "msg.h"
#include "vbuf_print.h"
#include "vstring.h"

/* vstring_extend - variable-length string buffer extension policy */

static void vstring_extend(VBUF *bp, ssize_t incr)
{
    size_t  used = bp->ptr - bp->data;
    ssize_t new_len;

    /*
     * Note: vp->vbuf.len is the current buffer size (both on entry and on
     * exit of this routine). We round up the increment size to the buffer
     * size to avoid silly little buffer increments. With really large
     * strings we might want to abandon the length doubling strategy, and go
     * to fixed increments.
     * 
     * The length overflow tests here and in vstring_alloc() should protect us
     * against all length overflow problems within vstring library routines.
     * 
     * Safety net: add a gratuitous null terminator so that C-style string
     * operations won't scribble past the end.
     */
    if ((bp->flags & VSTRING_FLAG_EXACT) == 0 && bp->len > incr)
    incr = bp->len;
    if (bp->len > SSIZE_T_MAX - incr - 1)
    msg_fatal("vstring_extend: length overflow");
    new_len = bp->len + incr;
    bp->data = (unsigned char *) myrealloc((void *) bp->data, new_len + 1);
    bp->data[new_len] = 0;
    bp->len = new_len;
    bp->ptr = bp->data + used;
    bp->cnt = bp->len - used;
}

/* vstring_buf_get_ready - vbuf callback for read buffer empty condition */

static int vstring_buf_get_ready(VBUF *unused_buf)
{
    msg_panic("vstring_buf_get: write-only buffer");
}

/* vstring_buf_put_ready - vbuf callback for write buffer full condition */

static int vstring_buf_put_ready(VBUF *bp)
{
    vstring_extend(bp, 1);
    return (0);
}

/* vstring_buf_space - vbuf callback to reserve space */

static int vstring_buf_space(VBUF *bp, ssize_t len)
{
    ssize_t need;

    if (len < 0)
    msg_panic("vstring_buf_space: bad length %ld", (long) len);
    if ((need = len - bp->cnt) > 0)
    vstring_extend(bp, need);
    return (0);
}

/* vstring_alloc - create variable-length string */

VSTRING *vstring_alloc(ssize_t len)
{
    VSTRING *vp;

    /*
     * Safety net: add a gratuitous null terminator so that C-style string
     * operations won't scribble past the end.
     */
    if (len < 1 || len > SSIZE_T_MAX - 1)
    msg_panic("vstring_alloc: bad length %ld", (long) len);
    vp = (VSTRING *) mymalloc(sizeof(*vp));
    vp->vbuf.flags = 0;
    vp->vbuf.len = 0;
    vp->vbuf.data = (unsigned char *) mymalloc(len + 1);
    vp->vbuf.data[len] = 0;
    vp->vbuf.len = len;
    VSTRING_RESET(vp);
    vp->vbuf.data[0] = 0;
    vp->vbuf.get_ready = vstring_buf_get_ready;
    vp->vbuf.put_ready = vstring_buf_put_ready;
    vp->vbuf.space = vstring_buf_space;
    vp->maxlen = 0;
    return (vp);
}

/* vstring_free - destroy variable-length string */

VSTRING *vstring_free(VSTRING *vp)
{
    if (vp->vbuf.data)
    myfree((void *) vp->vbuf.data);
    myfree((void *) vp);
    return (0);
}

/* vstring_ctl - modify memory management policy */

void    vstring_ctl(VSTRING *vp,...)
{
    va_list ap;
    int     code;

    va_start(ap, vp);
    while ((code = va_arg(ap, int)) != VSTRING_CTL_END) {
    switch (code) {
    default:
        msg_panic("vstring_ctl: unknown code: %d", code);
    case VSTRING_CTL_MAXLEN:
        vp->maxlen = va_arg(ap, ssize_t);
        if (vp->maxlen < 0)
        msg_panic("vstring_ctl: bad max length %ld", (long) vp->maxlen);
        break;
    case VSTRING_CTL_EXACT:
        vp->vbuf.flags |= VSTRING_FLAG_EXACT;
        break;
    }
    }
    va_end(ap);
}

/* vstring_truncate - truncate string */

VSTRING *vstring_truncate(VSTRING *vp, ssize_t len)
{
    ssize_t move;

    if (len < 0) {
    len = (-len);
    if ((move = VSTRING_LEN(vp) - len) > 0)
        memmove(vstring_str(vp), vstring_str(vp) + move, len);
    }
    if (len < VSTRING_LEN(vp))
    VSTRING_AT_OFFSET(vp, len);
    return (vp);
}

/* vstring_strcpy - copy string */

VSTRING *vstring_strcpy(VSTRING *vp, const char *src)
{
    VSTRING_RESET(vp);

    while (*src) {
    VSTRING_ADDCH(vp, *src);
    src++;
    }
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_strncpy - copy string of limited length */

VSTRING *vstring_strncpy(VSTRING *vp, const char *src, ssize_t len)
{
    VSTRING_RESET(vp);

    while (len-- > 0 && *src) {
    VSTRING_ADDCH(vp, *src);
    src++;
    }
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_strcat - append string */

VSTRING *vstring_strcat(VSTRING *vp, const char *src)
{
    while (*src) {
    VSTRING_ADDCH(vp, *src);
    src++;
    }
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_strncat - append string of limited length */

VSTRING *vstring_strncat(VSTRING *vp, const char *src, ssize_t len)
{
    while (len-- > 0 && *src) {
    VSTRING_ADDCH(vp, *src);
    src++;
    }
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_memcpy - copy buffer of limited length */

VSTRING *vstring_memcpy(VSTRING *vp, const char *src, ssize_t len)
{
    VSTRING_RESET(vp);

    VSTRING_SPACE(vp, len);
    memcpy(vstring_str(vp), src, len);
    VSTRING_AT_OFFSET(vp, len);
    return (vp);
}

/* vstring_memcat - append buffer of limited length */

VSTRING *vstring_memcat(VSTRING *vp, const char *src, ssize_t len)
{
    VSTRING_SPACE(vp, len);
    memcpy(vstring_end(vp), src, len);
    len += VSTRING_LEN(vp);
    VSTRING_AT_OFFSET(vp, len);
    return (vp);
}

/* vstring_memchr - locate byte in buffer */

char   *vstring_memchr(VSTRING *vp, int ch)
{
    unsigned char *cp;

    for (cp = (unsigned char *) vstring_str(vp); cp < (unsigned char *) vstring_end(vp); cp++)
    if (*cp == ch)
        return ((char *) cp);
    return (0);
}

/* vstring_insert - insert text into string */

VSTRING *vstring_insert(VSTRING *vp, ssize_t start, const char *buf, ssize_t len)
{
    ssize_t new_len;

    /*
     * Sanity check.
     */
    if (start < 0 || start >= VSTRING_LEN(vp))
    msg_panic("vstring_insert: bad start %ld", (long) start);
    if (len < 0)
    msg_panic("vstring_insert: bad length %ld", (long) len);

    /*
     * Move the existing content and copy the new content.
     */
    new_len = VSTRING_LEN(vp) + len;
    VSTRING_SPACE(vp, len);
    memmove(vstring_str(vp) + start + len, vstring_str(vp) + start,
        VSTRING_LEN(vp) - start);
    memcpy(vstring_str(vp) + start, buf, len);
    VSTRING_AT_OFFSET(vp, new_len);
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_prepend - prepend text to string */

VSTRING *vstring_prepend(VSTRING *vp, const char *buf, ssize_t len)
{
    ssize_t new_len;

    /*
     * Sanity check.
     */
    if (len < 0)
    msg_panic("vstring_prepend: bad length %ld", (long) len);

    /*
     * Move the existing content and copy the new content.
     */
    new_len = VSTRING_LEN(vp) + len;
    VSTRING_SPACE(vp, len);
    memmove(vstring_str(vp) + len, vstring_str(vp), VSTRING_LEN(vp));
    memcpy(vstring_str(vp), buf, len);
    VSTRING_AT_OFFSET(vp, new_len);
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_export - VSTRING to bare string */

char   *vstring_export(VSTRING *vp)
{
    char   *cp;

    cp = (char *) vp->vbuf.data;
    vp->vbuf.data = 0;
    myfree((void *) vp);
    return (cp);
}

/* vstring_import - bare string to vstring */

VSTRING *vstring_import(char *str)
{
    VSTRING *vp;
    ssize_t len;

    vp = (VSTRING *) mymalloc(sizeof(*vp));
    len = strlen(str);
    vp->vbuf.flags = 0;
    vp->vbuf.len = 0;
    vp->vbuf.data = (unsigned char *) str;
    vp->vbuf.len = len + 1;
    VSTRING_AT_OFFSET(vp, len);
    vp->vbuf.get_ready = vstring_buf_get_ready;
    vp->vbuf.put_ready = vstring_buf_put_ready;
    vp->vbuf.space = vstring_buf_space;
    vp->maxlen = 0;
    return (vp);
}

/* vstring_sprintf - formatted string */

VSTRING *vstring_sprintf(VSTRING *vp, const char *format,...)
{
    va_list ap;

    va_start(ap, format);
    vp = vstring_vsprintf(vp, format, ap);
    va_end(ap);
    return (vp);
}

/* vstring_vsprintf - format string, vsprintf-like interface */

VSTRING *vstring_vsprintf(VSTRING *vp, const char *format, va_list ap)
{
    VSTRING_RESET(vp);
    vbuf_print(&vp->vbuf, format, ap);
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_sprintf_append - append formatted string */

VSTRING *vstring_sprintf_append(VSTRING *vp, const char *format,...)
{
    va_list ap;

    va_start(ap, format);
    vp = vstring_vsprintf_append(vp, format, ap);
    va_end(ap);
    return (vp);
}

/* vstring_vsprintf_append - format + append string, vsprintf-like interface */

VSTRING *vstring_vsprintf_append(VSTRING *vp, const char *format, va_list ap)
{
    vbuf_print(&vp->vbuf, format, ap);
    VSTRING_TERMINATE(vp);
    return (vp);
}

/* vstring_sprintf_prepend - format + prepend string, vsprintf-like interface */

VSTRING *vstring_sprintf_prepend(VSTRING *vp, const char *format,...)
{
    va_list ap;
    ssize_t old_len = VSTRING_LEN(vp);
    ssize_t result_len;

    /* Construct: old|new|free */
    va_start(ap, format);
    vp = vstring_vsprintf_append(vp, format, ap);
    va_end(ap);
    result_len = VSTRING_LEN(vp);

    /* Construct: old|new|old|free */
    VSTRING_SPACE(vp, old_len);
    vstring_memcat(vp, vstring_str(vp), old_len);

    /* Construct: new|old|free */
    memmove(vstring_str(vp), vstring_str(vp) + old_len, result_len);
    VSTRING_AT_OFFSET(vp, result_len);
    VSTRING_TERMINATE(vp);
    return (vp);
}

#ifdef TEST

 /*
  * Test program - concatenate all command-line arguments into one string.
  */
#include <stdio.h>

int     main(int argc, char **argv)
{
    VSTRING *vp = vstring_alloc(1);
    int     n;

    /*
     * Report the location of the gratuitous null terminator.
     */
    for (n = 1; n <= 5; n++) {
    VSTRING_ADDCH(vp, 'x');
    printf("payload/buffer size %d/%ld, strlen() %ld\n",
           n, (long) (vp)->vbuf.len, (long) strlen(vstring_str(vp)));
    }

    VSTRING_RESET(vp);
    while (argc-- > 0) {
    vstring_strcat(vp, *argv++);
    vstring_strcat(vp, ".");
    }
    printf("argv concatenated: %s\n", vstring_str(vp));
    vstring_free(vp);
    return (0);
}

#endif