#include "cache.h"
#include "refs.h"
#include "utf8.h"

int starts_with(const char *str, const char *prefix)
{
        for (; ; str++, prefix++)
                if (!*prefix)
                        return 1;
                else if (*str != *prefix)
                        return 0;
}

/*
 * 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];

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

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

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

void strbuf_attach(struct strbuf *sb, void *buf, size_t len, size_t alloc)
{
        strbuf_release(sb);
        sb->buf   = buf;
        sb->len   = len;
        sb->alloc = alloc;
        strbuf_grow(sb, 0);
        sb->buf[sb->len] = '\0';
}

void strbuf_grow(struct strbuf *sb, size_t extra)
{
        int new_buf = !sb->alloc;
        if (unsigned_add_overflows(extra, 1) ||
            unsigned_add_overflows(sb->len, extra + 1))
                die("you want to use way too much memory");
        if (new_buf)
                sb->buf = NULL;
        ALLOC_GROW(sb->buf, sb->len + extra + 1, sb->alloc);
        if (new_buf)
                sb->buf[0] = '\0';
}

void strbuf_trim(struct strbuf *sb)
{
        strbuf_rtrim(sb);
        strbuf_ltrim(sb);
}
void strbuf_rtrim(struct strbuf *sb)
{
        while (sb->len > 0 && isspace((unsigned char)sb->buf[sb->len - 1]))
                sb->len--;
        sb->buf[sb->len] = '\0';
}

void strbuf_ltrim(struct strbuf *sb)
{
        char *b = sb->buf;
        while (sb->len > 0 && isspace(*b)) {
                b++;
                sb->len--;
        }
        memmove(sb->buf, b, sb->len);
        sb->buf[sb->len] = '\0';
}

int strbuf_reencode(struct strbuf *sb, const char *from, const char *to)
{
        char *out;
        int len;

        if (same_encoding(from, to))
                return 0;

        out = reencode_string_len(sb->buf, sb->len, to, from, &len);
        if (!out)
                return -1;

        strbuf_attach(sb, out, len, len);
        return 0;
}

void strbuf_tolower(struct strbuf *sb)
{
        char *p = sb->buf, *end = sb->buf + sb->len;
        for (; p < end; p++)
                *p = tolower(*p);
}

struct strbuf **strbuf_split_buf(const char *str, size_t slen,
                                 int terminator, int max)
{
        struct strbuf **ret = NULL;
        size_t nr = 0, alloc = 0;
        struct strbuf *t;

        while (slen) {
                int len = slen;
                if (max <= 0 || nr + 1 < max) {
                        const char *end = memchr(str, terminator, slen);
                        if (end)
                                len = end - str + 1;
                }
                t = xmalloc(sizeof(struct strbuf));
                strbuf_init(t, len);
                strbuf_add(t, str, len);
                ALLOC_GROW(ret, nr + 2, alloc);
                ret[nr++] = t;
                str += len;
                slen -= len;
        }
        ALLOC_GROW(ret, nr + 1, alloc); /* In case string was empty */
        ret[nr] = NULL;
        return ret;
}

void strbuf_list_free(struct strbuf **sbs)
{
        struct strbuf **s = sbs;

        while (*s) {
                strbuf_release(*s);
                free(*s++);
        }
        free(sbs);
}

int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
{
        int len = a->len < b->len ? a->len: b->len;
        int cmp = memcmp(a->buf, b->buf, len);
        if (cmp)
                return cmp;
        return a->len < b->len ? -1: a->len != b->len;
}

void strbuf_splice(struct strbuf *sb, size_t pos, size_t len,
                                   const void *data, size_t dlen)
{
        if (unsigned_add_overflows(pos, len))
                die("you want to use way too much memory");
        if (pos > sb->len)
                die("`pos' is too far after the end of the buffer");
        if (pos + len > sb->len)
                die("`pos + len' is too far after the end of the buffer");

        if (dlen >= len)
                strbuf_grow(sb, dlen - len);
        memmove(sb->buf + pos + dlen,
                        sb->buf + pos + len,
                        sb->len - pos - len);
        memcpy(sb->buf + pos, data, dlen);
        strbuf_setlen(sb, sb->len + dlen - len);
}

void strbuf_insert(struct strbuf *sb, size_t pos, const void *data, size_t len)
{
        strbuf_splice(sb, pos, 0, data, len);
}

void strbuf_remove(struct strbuf *sb, size_t pos, size_t len)
{
        strbuf_splice(sb, pos, len, "", 0);
}

void strbuf_add(struct strbuf *sb, const void *data, size_t len)
{
        strbuf_grow(sb, len);
        memcpy(sb->buf + sb->len, data, len);
        strbuf_setlen(sb, sb->len + len);
}

void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2)
{
        strbuf_grow(sb, sb2->len);
        memcpy(sb->buf + sb->len, sb2->buf, sb2->len);
        strbuf_setlen(sb, sb->len + sb2->len);
}

void strbuf_adddup(struct strbuf *sb, size_t pos, size_t len)
{
        strbuf_grow(sb, len);
        memcpy(sb->buf + sb->len, sb->buf + pos, len);
        strbuf_setlen(sb, sb->len + len);
}

void strbuf_addchars(struct strbuf *sb, int c, size_t n)
{
        strbuf_grow(sb, n);
        memset(sb->buf + sb->len, c, n);
        strbuf_setlen(sb, sb->len + n);
}

void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
{
        va_list ap;
        va_start(ap, fmt);
        strbuf_vaddf(sb, fmt, ap);
        va_end(ap);
}

static void add_lines(struct strbuf *out,
                        const char *prefix1,
                        const char *prefix2,
                        const char *buf, size_t size)
{
        while (size) {
                const char *prefix;
                const char *next = memchr(buf, '\n', size);
                next = next ? (next + 1) : (buf + size);

                prefix = ((prefix2 && (buf[0] == '\n' || buf[0] == '\t'))
                          ? prefix2 : prefix1);
                strbuf_addstr(out, prefix);
                strbuf_add(out, buf, next - buf);
                size -= next - buf;
                buf = next;
        }
        strbuf_complete_line(out);
}

void strbuf_add_commented_lines(struct strbuf *out, const char *buf, size_t size)
{
        static char prefix1[3];
        static char prefix2[2];

        if (prefix1[0] != comment_line_char) {
                xsnprintf(prefix1, sizeof(prefix1), "%c ", comment_line_char);
                xsnprintf(prefix2, sizeof(prefix2), "%c", comment_line_char);
        }
        add_lines(out, prefix1, prefix2, buf, size);
}

void strbuf_commented_addf(struct strbuf *sb, const char *fmt, ...)
{
        va_list params;
        struct strbuf buf = STRBUF_INIT;
        int incomplete_line = sb->len && sb->buf[sb->len - 1] != '\n';

        va_start(params, fmt);
        strbuf_vaddf(&buf, fmt, params);
        va_end(params);

        strbuf_add_commented_lines(sb, buf.buf, buf.len);
        if (incomplete_line)
                sb->buf[--sb->len] = '\0';

        strbuf_release(&buf);
}

void strbuf_vaddf(struct strbuf *sb, const char *fmt, va_list ap)
{
        int len;
        va_list cp;

        if (!strbuf_avail(sb))
                strbuf_grow(sb, 64);
        va_copy(cp, ap);
        len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, cp);
        va_end(cp);
        if (len < 0)
                die("BUG: your vsnprintf is broken (returned %d)", len);
        if (len > strbuf_avail(sb)) {
                strbuf_grow(sb, len);
                len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
                if (len > strbuf_avail(sb))
                        die("BUG: your vsnprintf is broken (insatiable)");
        }
        strbuf_setlen(sb, sb->len + len);
}

void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
                   void *context)
{
        for (;;) {
                const char *percent;
                size_t consumed;

                percent = strchrnul(format, '%');
                strbuf_add(sb, format, percent - format);
                if (!*percent)
                        break;
                format = percent + 1;

                if (*format == '%') {
                        strbuf_addch(sb, '%');
                        format++;
                        continue;
                }

                consumed = fn(sb, format, context);
                if (consumed)
                        format += consumed;
                else
                        strbuf_addch(sb, '%');
        }
}

size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
                void *context)
{
        struct strbuf_expand_dict_entry *e = context;
        size_t len;

        for (; e->placeholder && (len = strlen(e->placeholder)); e++) {
                if (!strncmp(placeholder, e->placeholder, len)) {
                        if (e->value)
                                strbuf_addstr(sb, e->value);
                        return len;
                }
        }
        return 0;
}

void strbuf_addbuf_percentquote(struct strbuf *dst, const struct strbuf *src)
{
        int i, len = src->len;

        for (i = 0; i < len; i++) {
                if (src->buf[i] == '%')
                        strbuf_addch(dst, '%');
                strbuf_addch(dst, src->buf[i]);
        }
}

size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f)
{
        size_t res;
        size_t oldalloc = sb->alloc;

        strbuf_grow(sb, size);
        res = fread(sb->buf + sb->len, 1, size, f);
        if (res > 0)
                strbuf_setlen(sb, sb->len + res);
        else if (oldalloc == 0)
                strbuf_release(sb);
        return res;
}

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

        strbuf_grow(sb, hint ? hint : 8192);
        for (;;) {
                ssize_t want = sb->alloc - sb->len - 1;
                ssize_t got = read_in_full(fd, sb->buf + sb->len, want);

                if (got < 0) {
                        if (oldalloc == 0)
                                strbuf_release(sb);
                        else
                                strbuf_setlen(sb, oldlen);
                        return -1;
                }
                sb->len += got;
                if (got < want)
                        break;
                strbuf_grow(sb, 8192);
        }

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

ssize_t strbuf_read_once(struct strbuf *sb, int fd, size_t hint)
{
        ssize_t cnt;

        strbuf_grow(sb, hint ? hint : 8192);
        cnt = xread(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
        if (cnt > 0)
                strbuf_setlen(sb, sb->len + cnt);
        return cnt;
}

ssize_t strbuf_write(struct strbuf *sb, FILE *f)
{
        return sb->len ? fwrite(sb->buf, 1, sb->len, f) : 0;
}


#define STRBUF_MAXLINK (2*PATH_MAX)

int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
{
        size_t oldalloc = sb->alloc;

        if (hint < 32)
                hint = 32;

        while (hint < STRBUF_MAXLINK) {
                int len;

                strbuf_grow(sb, hint);
                len = readlink(path, sb->buf, hint);
                if (len < 0) {
                        if (errno != ERANGE)
                                break;
                } else if (len < hint) {
                        strbuf_setlen(sb, len);
                        return 0;
                }

                /* .. the buffer was too small - try again */
                hint *= 2;
        }
        if (oldalloc == 0)
                strbuf_release(sb);
        return -1;
}

int strbuf_getcwd(struct strbuf *sb)
{
        size_t oldalloc = sb->alloc;
        size_t guessed_len = 128;

        for (;; guessed_len *= 2) {
                strbuf_grow(sb, guessed_len);
                if (getcwd(sb->buf, sb->alloc)) {
                        strbuf_setlen(sb, strlen(sb->buf));
                        return 0;
                }
                if (errno != ERANGE)
                        break;
        }
        if (oldalloc == 0)
                strbuf_release(sb);
        else
                strbuf_reset(sb);
        return -1;
}

#ifdef HAVE_GETDELIM
int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
{
        ssize_t r;

        if (feof(fp))
                return EOF;

        strbuf_reset(sb);

        /* Translate slopbuf to NULL, as we cannot call realloc on it */
        if (!sb->alloc)
                sb->buf = NULL;
        r = getdelim(&sb->buf, &sb->alloc, term, fp);

        if (r > 0) {
                sb->len = r;
                return 0;
        }
        assert(r == -1);

        /*
         * Normally we would have called xrealloc, which will try to free
         * memory and recover. But we have no way to tell getdelim() to do so.
         * Worse, we cannot try to recover ENOMEM ourselves, because we have
         * no idea how many bytes were read by getdelim.
         *
         * Dying here is reasonable. It mirrors what xrealloc would do on
         * catastrophic memory failure. We skip the opportunity to free pack
         * memory and retry, but that's unlikely to help for a malloc small
         * enough to hold a single line of input, anyway.
         */
        if (errno == ENOMEM)
                die("Out of memory, getdelim failed");

        /*
         * Restore strbuf invariants; if getdelim left us with a NULL pointer,
         * we can just re-init, but otherwise we should make sure that our
         * length is empty, and that the result is NUL-terminated.
         */
        if (!sb->buf)
                strbuf_init(sb, 0);
        else
                strbuf_reset(sb);
        return EOF;
}
#else
int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
{
        int ch;

        if (feof(fp))
                return EOF;

        strbuf_reset(sb);
        flockfile(fp);
        while ((ch = getc_unlocked(fp)) != EOF) {
                if (!strbuf_avail(sb))
                        strbuf_grow(sb, 1);
                sb->buf[sb->len++] = ch;
                if (ch == term)
                        break;
        }
        funlockfile(fp);
        if (ch == EOF && sb->len == 0)
                return EOF;

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

static int strbuf_getdelim(struct strbuf *sb, FILE *fp, int term)
{
        if (strbuf_getwholeline(sb, fp, term))
                return EOF;
        if (sb->buf[sb->len - 1] == term)
                strbuf_setlen(sb, sb->len - 1);
        return 0;
}

int strbuf_getline(struct strbuf *sb, FILE *fp)
{
        if (strbuf_getwholeline(sb, fp, '\n'))
                return EOF;
        if (sb->buf[sb->len - 1] == '\n') {
                strbuf_setlen(sb, sb->len - 1);
                if (sb->len && sb->buf[sb->len - 1] == '\r')
                        strbuf_setlen(sb, sb->len - 1);
        }
        return 0;
}

int strbuf_getline_lf(struct strbuf *sb, FILE *fp)
{
        return strbuf_getdelim(sb, fp, '\n');
}

int strbuf_getline_nul(struct strbuf *sb, FILE *fp)
{
        return strbuf_getdelim(sb, fp, '\0');
}

int strbuf_getwholeline_fd(struct strbuf *sb, int fd, int term)
{
        strbuf_reset(sb);

        while (1) {
                char ch;
                ssize_t len = xread(fd, &ch, 1);
                if (len <= 0)
                        return EOF;
                strbuf_addch(sb, ch);
                if (ch == term)
                        break;
        }
        return 0;
}

ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
{
        int fd;
        ssize_t len;

        fd = open(path, O_RDONLY);
        if (fd < 0)
                return -1;
        len = strbuf_read(sb, fd, hint);
        close(fd);
        if (len < 0)
                return -1;

        return len;
}

void strbuf_add_lines(struct strbuf *out, const char *prefix,
                      const char *buf, size_t size)
{
        add_lines(out, prefix, NULL, buf, size);
}

void strbuf_addstr_xml_quoted(struct strbuf *buf, const char *s)
{
        while (*s) {
                size_t len = strcspn(s, "\"<>&");
                strbuf_add(buf, s, len);
                s += len;
                switch (*s) {
                case '"':
                        strbuf_addstr(buf, "&quot;");
                        break;
                case '<':
                        strbuf_addstr(buf, "&lt;");
                        break;
                case '>':
                        strbuf_addstr(buf, "&gt;");
                        break;
                case '&':
                        strbuf_addstr(buf, "&amp;");
                        break;
                case 0:
                        return;
                }
                s++;
        }
}

static int is_rfc3986_reserved(char ch)
{
        switch (ch) {
                case '!': case '*': case '\'': case '(': case ')': case ';':
                case ':': case '@': case '&': case '=': case '+': case '$':
                case ',': case '/': case '?': case '#': case '[': case ']':
                        return 1;
        }
        return 0;
}

static int is_rfc3986_unreserved(char ch)
{
        return isalnum(ch) ||
                ch == '-' || ch == '_' || ch == '.' || ch == '~';
}

static void strbuf_add_urlencode(struct strbuf *sb, const char *s, size_t len,
                                 int reserved)
{
        strbuf_grow(sb, len);
        while (len--) {
                char ch = *s++;
                if (is_rfc3986_unreserved(ch) ||
                    (!reserved && is_rfc3986_reserved(ch)))
                        strbuf_addch(sb, ch);
                else
                        strbuf_addf(sb, "%%%02x", ch);
        }
}

void strbuf_addstr_urlencode(struct strbuf *sb, const char *s,
                             int reserved)
{
        strbuf_add_urlencode(sb, s, strlen(s), reserved);
}

void strbuf_humanise_bytes(struct strbuf *buf, off_t bytes)
{
        if (bytes > 1 << 30) {
                strbuf_addf(buf, "%u.%2.2u GiB",
                            (int)(bytes >> 30),
                            (int)(bytes & ((1 << 30) - 1)) / 10737419);
        } else if (bytes > 1 << 20) {
                int x = bytes + 5243;  /* for rounding */
                strbuf_addf(buf, "%u.%2.2u MiB",
                            x >> 20, ((x & ((1 << 20) - 1)) * 100) >> 20);
        } else if (bytes > 1 << 10) {
                int x = bytes + 5;  /* for rounding */
                strbuf_addf(buf, "%u.%2.2u KiB",
                            x >> 10, ((x & ((1 << 10) - 1)) * 100) >> 10);
        } else {
                strbuf_addf(buf, "%u bytes", (int)bytes);
        }
}

void strbuf_add_absolute_path(struct strbuf *sb, const char *path)
{
        if (!*path)
                die("The empty string is not a valid path");
        if (!is_absolute_path(path)) {
                struct stat cwd_stat, pwd_stat;
                size_t orig_len = sb->len;
                char *cwd = xgetcwd();
                char *pwd = getenv("PWD");
                if (pwd && strcmp(pwd, cwd) &&
                    !stat(cwd, &cwd_stat) &&
                    (cwd_stat.st_dev || cwd_stat.st_ino) &&
                    !stat(pwd, &pwd_stat) &&
                    pwd_stat.st_dev == cwd_stat.st_dev &&
                    pwd_stat.st_ino == cwd_stat.st_ino)
                        strbuf_addstr(sb, pwd);
                else
                        strbuf_addstr(sb, cwd);
                if (sb->len > orig_len && !is_dir_sep(sb->buf[sb->len - 1]))
                        strbuf_addch(sb, '/');
                free(cwd);
        }
        strbuf_addstr(sb, path);
}

int printf_ln(const char *fmt, ...)
{
        int ret;
        va_list ap;
        va_start(ap, fmt);
        ret = vprintf(fmt, ap);
        va_end(ap);
        if (ret < 0 || putchar('\n') == EOF)
                return -1;
        return ret + 1;
}

int fprintf_ln(FILE *fp, const char *fmt, ...)
{
        int ret;
        va_list ap;
        va_start(ap, fmt);
        ret = vfprintf(fp, fmt, ap);
        va_end(ap);
        if (ret < 0 || putc('\n', fp) == EOF)
                return -1;
        return ret + 1;
}

char *xstrdup_tolower(const char *string)
{
        char *result;
        size_t len, i;

        len = strlen(string);
        result = xmallocz(len);
        for (i = 0; i < len; i++)
                result[i] = tolower(string[i]);
        result[i] = '\0';
        return result;
}

char *xstrvfmt(const char *fmt, va_list ap)
{
        struct strbuf buf = STRBUF_INIT;
        strbuf_vaddf(&buf, fmt, ap);
        return strbuf_detach(&buf, NULL);
}

char *xstrfmt(const char *fmt, ...)
{
        va_list ap;
        char *ret;

        va_start(ap, fmt);
        ret = xstrvfmt(fmt, ap);
        va_end(ap);

        return ret;
}

void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm)
{
        size_t hint = 128;
        size_t len;

        if (!*fmt)
                return;

        strbuf_grow(sb, hint);
        len = strftime(sb->buf + sb->len, sb->alloc - sb->len, fmt, tm);

        if (!len) {
                /*
                 * strftime reports "0" if it could not fit the result in the buffer.
                 * Unfortunately, it also reports "0" if the requested time string
                 * takes 0 bytes. So our strategy is to munge the format so that the
                 * output contains at least one character, and then drop the extra
                 * character before returning.
                 */
                struct strbuf munged_fmt = STRBUF_INIT;
                strbuf_addf(&munged_fmt, "%s ", fmt);
                while (!len) {
                        hint *= 2;
                        strbuf_grow(sb, hint);
                        len = strftime(sb->buf + sb->len, sb->alloc - sb->len,
                                       munged_fmt.buf, tm);
                }
                strbuf_release(&munged_fmt);
                len--; /* drop munged space */
        }
        strbuf_setlen(sb, sb->len + len);
}

void strbuf_add_unique_abbrev(struct strbuf *sb, const unsigned char *sha1,
                              int abbrev_len)
{
        int r;
        strbuf_grow(sb, GIT_SHA1_HEXSZ + 1);
        r = find_unique_abbrev_r(sb->buf + sb->len, sha1, abbrev_len);
        strbuf_setlen(sb, sb->len + r);
}

/*
 * Returns the length of a line, without trailing spaces.
 *
 * If the line ends with newline, it will be removed too.
 */
static size_t cleanup(char *line, size_t len)
{
        while (len) {
                unsigned char c = line[len - 1];
                if (!isspace(c))
                        break;
                len--;
        }

        return len;
}

/*
 * Remove empty lines from the beginning and end
 * and also trailing spaces from every line.
 *
 * Turn multiple consecutive empty lines between paragraphs
 * into just one empty line.
 *
 * If the input has only empty lines and spaces,
 * no output will be produced.
 *
 * If last line does not have a newline at the end, one is added.
 *
 * Enable skip_comments to skip every line starting with comment
 * character.
 */
void strbuf_stripspace(struct strbuf *sb, int skip_comments)
{
        int empties = 0;
        size_t i, j, len, newlen;
        char *eol;

        /* We may have to add a newline. */
        strbuf_grow(sb, 1);

        for (i = j = 0; i < sb->len; i += len, j += newlen) {
                eol = memchr(sb->buf + i, '\n', sb->len - i);
                len = eol ? eol - (sb->buf + i) + 1 : sb->len - i;

                if (skip_comments && len && sb->buf[i] == comment_line_char) {
                        newlen = 0;
                        continue;
                }
                newlen = cleanup(sb->buf + i, len);

                /* Not just an empty line? */
                if (newlen) {
                        if (empties > 0 && j > 0)
                                sb->buf[j++] = '\n';
                        empties = 0;
                        memmove(sb->buf + j, sb->buf + i, newlen);
                        sb->buf[newlen + j++] = '\n';
                } else {
                        empties++;
                }
        }

        strbuf_setlen(sb, j);
}

int strbuf_normalize_path(struct strbuf *src)
{
        struct strbuf dst = STRBUF_INIT;

        strbuf_grow(&dst, src->len);
        if (normalize_path_copy(dst.buf, src->buf) < 0) {
                strbuf_release(&dst);
                return -1;
        }

        /*
         * normalize_path does not tell us the new length, so we have to
         * compute it by looking for the new NUL it placed
         */
        strbuf_setlen(&dst, strlen(dst.buf));
        strbuf_swap(src, &dst);
        strbuf_release(&dst);
        return 0;
}