// SPDX-License-Identifier: GPL-2.0
#include "cache.h"
#include "debug.h"
#include "strbuf.h"
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/zalloc.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.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) {
                va_end(ap_saved);
                return len;
        }
        if (len > strbuf_avail(sb)) {
                ret = strbuf_grow(sb, len);
                if (ret) {
                        va_end(ap_saved);
                        return ret;
                }
                len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap_saved);
                if (len > strbuf_avail(sb)) {
                        pr_debug("this should not happen, your vsnprintf is broken");
                        va_end(ap_saved);
                        return -EINVAL;
                }
        }
        va_end(ap_saved);
        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;
}