utun2/lib/strbuf.c

/*
 * strbuf.c — safe growable printf buffer
 */
#include "strbuf.h"
#include "mem.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define STRBUF_MIN_CAP  16

void strbuf_init(struct strbuf *sb, size_t initial_cap) {
    if (initial_cap < STRBUF_MIN_CAP) initial_cap = STRBUF_MIN_CAP;
    sb->buf = u_malloc(initial_cap);
    if (sb->buf) { sb->buf[0] = '\0'; sb->cap = initial_cap; }
    else         { sb->cap = 0; }
    sb->len = 0;
}

void strbuf_free(struct strbuf *sb) {
    if (sb->buf) { u_free(sb->buf); sb->buf = NULL; }
    sb->cap = 0; sb->len = 0;
}

char *strbuf_detach(struct strbuf *sb) {
    char *ret = sb->buf;
    sb->buf = NULL; sb->cap = 0; sb->len = 0;
    return ret;
}

void strbuf_reset(struct strbuf *sb) {
    if (sb->buf) sb->buf[0] = '\0';
    sb->len = 0;
}

static int strbuf_grow(struct strbuf *sb, size_t need) {
    size_t nc = sb->cap ? sb->cap : STRBUF_MIN_CAP;
    while (nc < need) { nc *= 2; if (nc < STRBUF_MIN_CAP) return -1; }
    char *n = u_realloc(sb->buf, nc);
    if (!n) return -1;
    sb->buf = n; sb->cap = nc;
    return 0;
}

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

    /* measure */
    va_start(ap, fmt);
    int need = vsnprintf(NULL, 0, fmt, ap);
    va_end(ap);
    if (need < 0) { return -1; }

    /* grow */
    size_t want = sb->len + (size_t)need + 1;   /* +1 for '\0' */
    if (want > sb->cap && strbuf_grow(sb, want) < 0) return -1;

    /* write */
    va_start(ap, fmt);
    int w = vsnprintf(sb->buf + sb->len, sb->cap - sb->len, fmt, ap);
    va_end(ap);
    if (w > 0) sb->len += (size_t)w;
    return w;
}

void strbuf_addc(struct strbuf *sb, char c) {
    if (sb->len + 2 > sb->cap && strbuf_grow(sb, sb->len + 2) < 0) return;
    sb->buf[sb->len++] = c;
    sb->buf[sb->len]   = '\0';
}

void strbuf_adds(struct strbuf *sb, const char *s) {
    if (!s) return;
    size_t slen = strlen(s);
    if (sb->len + slen + 1 > sb->cap && strbuf_grow(sb, sb->len + slen + 1) < 0) return;
    memcpy(sb->buf + sb->len, s, slen);
    sb->len += slen;
    sb->buf[sb->len] = '\0';
}