strbuf.c

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// SPDX-License-Identifier: GPL-2.0
#include "debug.h"
#include "util.h"
#include <linux/kernel.h>
#include <errno.h>

/*
 * Used as the default ->buf value, so that people can always assume
 * buf is non NULL and ->buf is NUL terminated even for a freshly
 * initialized strbuf.
 */
char strbuf_slopbuf[1];

int strbuf_init(struct strbuf *sb, ssize_t hint)
{
    sb->alloc = sb->len = 0;
    sb->buf = strbuf_slopbuf;
    if (hint)
        return strbuf_grow(sb, hint);
    return 0;
}

void strbuf_release(struct strbuf *sb)
{
    if (sb->alloc) {
        zfree(&sb->buf);
        strbuf_init(sb, 0);
    }
}

char *strbuf_detach(struct strbuf *sb, size_t *sz)
{
    char *res = sb->alloc ? sb->buf : NULL;
    if (sz)
        *sz = sb->len;
    strbuf_init(sb, 0);
    return res;
}

int strbuf_grow(struct strbuf *sb, size_t extra)
{
    char *buf;
    size_t nr = sb->len + extra + 1;

    if (nr < sb->alloc)
        return 0;

    if (nr <= sb->len)
        return -E2BIG;

    if (alloc_nr(sb->alloc) > nr)
        nr = alloc_nr(sb->alloc);

    /*
     * Note that sb->buf == strbuf_slopbuf if sb->alloc == 0, and it is
     * a static variable. Thus we have to avoid passing it to realloc.
     */
    buf = realloc(sb->alloc ? sb->buf : NULL, nr * sizeof(*buf));
    if (!buf)
        return -ENOMEM;

    sb->buf = buf;
    sb->alloc = nr;
    return 0;
}

int strbuf_addch(struct strbuf *sb, int c)
{
    int ret = strbuf_grow(sb, 1);
    if (ret)
        return ret;

    sb->buf[sb->len++] = c;
    sb->buf[sb->len] = '\0';
    return 0;
}

int strbuf_add(struct strbuf *sb, const void *data, size_t len)
{
    int ret = strbuf_grow(sb, len);
    if (ret)
        return ret;

    memcpy(sb->buf + sb->len, data, len);
    return strbuf_setlen(sb, sb->len + len);
}

static int strbuf_addv(struct strbuf *sb, const char *fmt, va_list ap)
{
    int len, ret;
    va_list ap_saved;

    if (!strbuf_avail(sb)) {
        ret = strbuf_grow(sb, 64);
        if (ret)
            return ret;
    }

    va_copy(ap_saved, ap);
    len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
    if (len < 0)
        return len;
    if (len > strbuf_avail(sb)) {
        ret = strbuf_grow(sb, len);
        if (ret)
            return ret;
        len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap_saved);
        va_end(ap_saved);
        if (len > strbuf_avail(sb)) {
            pr_debug("this should not happen, your vsnprintf is broken");
            return -EINVAL;
        }
    }
    return strbuf_setlen(sb, sb->len + len);
}

int strbuf_addf(struct strbuf *sb, const char *fmt, ...)
{
    va_list ap;
    int ret;

    va_start(ap, fmt);
    ret = strbuf_addv(sb, fmt, ap);
    va_end(ap);
    return ret;
}

ssize_t strbuf_read(struct strbuf *sb, int fd, ssize_t hint)
{
    size_t oldlen = sb->len;
    size_t oldalloc = sb->alloc;
    int ret;

    ret = strbuf_grow(sb, hint ? hint : 8192);
    if (ret)
        return ret;

    for (;;) {
        ssize_t cnt;

        cnt = read(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
        if (cnt < 0) {
            if (oldalloc == 0)
                strbuf_release(sb);
            else
                strbuf_setlen(sb, oldlen);
            return cnt;
        }
        if (!cnt)
            break;
        sb->len += cnt;
        ret = strbuf_grow(sb, 8192);
        if (ret)
            return ret;
    }

    sb->buf[sb->len] = '\0';
    return sb->len - oldlen;
}