Rework strbuf API and semantics.

  The gory details are explained in strbuf.h. The change of semantics this
patch enforces is that the embeded buffer has always a '\0' character after
its last byte, to always make it a C-string. The offs-by-one changes are all
related to that very change.

  A strbuf can be used to store byte arrays, or as an extended string
library. The `buf' member can be passed to any C legacy string function,
because strbuf operations always ensure there is a terminating \0 at the end
of the buffer, not accounted in the `len' field of the structure.

  A strbuf can be used to generate a string/buffer whose final size is not
really known, and then "strbuf_detach" can be used to get the built buffer,
and keep the wrapping "strbuf" structure usable for further work again.

  Other interesting feature: strbuf_grow(sb, size) ensure that there is
enough allocated space in `sb' to put `size' new octets of data in the
buffer. It helps avoiding reallocating data for nothing when the problem the
strbuf helps to solve has a known typical size.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/archive-tar.c b/archive-tar.c
index 66fe3e375b545613faba4e051dc41c1acb5d8cee..a0763c5b5a0b1e0697bcc70623852174bc7a0a3b 100644 (file)
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -166,7 +166,7 @@ static void write_entry(const unsigned char *sha1, struct strbuf *path,
                sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
        } else {
                if (verbose)
-                       fprintf(stderr, "%.*s\n", path->len, path->buf);
+                       fprintf(stderr, "%.*s\n", (int)path->len, path->buf);
                if (S_ISDIR(mode) || S_ISGITLINK(mode)) {
                        *header.typeflag = TYPEFLAG_DIR;
                        mode = (mode | 0777) & ~tar_umask;

diff --git a/fast-import.c b/fast-import.c
index 078079d404d8245d73ea8ef36d764f2bb311d0a9..2f7baf4917097a5a40a981f9e62818f43492004f 100644 (file)
--- a/fast-import.c
+++ b/fast-import.c
@@ -1595,7 +1595,7 @@ static void read_next_command(void)
                } else {
                        struct recent_command *rc;
 
-                       command_buf.buf = NULL;
+                       strbuf_detach(&command_buf);
                        read_line(&command_buf, stdin, '\n');
                        if (command_buf.eof)
                                return;
@@ -1649,7 +1649,6 @@ static void *cmd_data (size_t *size)
                size_t sz = 8192, term_len = command_buf.len - 5 - 2;
                length = 0;
                buffer = xmalloc(sz);
-               command_buf.buf = NULL;
                for (;;) {
                        read_line(&command_buf, stdin, '\n');
                        if (command_buf.eof)
@@ -1657,11 +1656,11 @@ static void *cmd_data (size_t *size)
                        if (term_len == command_buf.len
                                && !strcmp(term, command_buf.buf))
                                break;
-                       ALLOC_GROW(buffer, length + command_buf.len, sz);
+                       ALLOC_GROW(buffer, length + command_buf.len + 1, sz);
                        memcpy(buffer + length,
                                command_buf.buf,
-                               command_buf.len - 1);
-                       length += command_buf.len - 1;
+                               command_buf.len);
+                       length += command_buf.len;
                        buffer[length++] = '\n';
                }
                free(term);
@@ -2101,7 +2100,7 @@ static void cmd_new_commit(void)
        }
 
        /* file_change* */
-       while (!command_buf.eof && command_buf.len > 1) {
+       while (!command_buf.eof && command_buf.len > 0) {
                if (!prefixcmp(command_buf.buf, "M "))
                        file_change_m(b);
                else if (!prefixcmp(command_buf.buf, "D "))
@@ -2256,7 +2255,7 @@ static void cmd_reset_branch(void)
        else
                b = new_branch(sp);
        read_next_command();
-       if (!cmd_from(b) && command_buf.len > 1)
+       if (!cmd_from(b) && command_buf.len > 0)
                unread_command_buf = 1;
 }
 
@@ -2273,7 +2272,7 @@ static void cmd_checkpoint(void)
 
 static void cmd_progress(void)
 {
-       fwrite(command_buf.buf, 1, command_buf.len - 1, stdout);
+       fwrite(command_buf.buf, 1, command_buf.len, stdout);
        fputc('\n', stdout);
        fflush(stdout);
        skip_optional_lf();

diff --git a/mktree.c b/mktree.c
index d86dde89d63e21994fd2538d5ac3a21ead3a7338..86de5eb5f6ed426c0f7b6b04d036389a543e9549 100644 (file)
--- a/mktree.c
+++ b/mktree.c
@@ -92,7 +92,6 @@ int main(int ac, char **av)
 
        strbuf_init(&sb);
        while (1) {
-               int len;
                char *ptr, *ntr;
                unsigned mode;
                enum object_type type;
@@ -101,7 +100,6 @@ int main(int ac, char **av)
                read_line(&sb, stdin, line_termination);
                if (sb.eof)
                        break;
-               len = sb.len;
                ptr = sb.buf;
                /* Input is non-recursive ls-tree output format
                 * mode SP type SP sha1 TAB name
@@ -111,7 +109,7 @@ int main(int ac, char **av)
                        die("input format error: %s", sb.buf);
                ptr = ntr + 1; /* type */
                ntr = strchr(ptr, ' ');
-               if (!ntr || sb.buf + len <= ntr + 41 ||
+               if (!ntr || sb.buf + sb.len <= ntr + 40 ||
                    ntr[41] != '\t' ||
                    get_sha1_hex(ntr + 1, sha1))
                        die("input format error: %s", sb.buf);

diff --git a/strbuf.c b/strbuf.c
index e33d06b87c978ad7484c9d6bf972681c3d6cdeb0..7136de14c63b0a93c271156fcef86ca26cecea7a 100644 (file)
--- a/strbuf.c
+++ b/strbuf.c
@@ -2,40 +2,113 @@
 #include "strbuf.h"
 
 void strbuf_init(struct strbuf *sb) {
-       sb->buf = NULL;
-       sb->eof = sb->alloc = sb->len = 0;
+       memset(sb, 0, sizeof(*sb));
 }
 
-static void strbuf_begin(struct strbuf *sb) {
+void strbuf_release(struct strbuf *sb) {
        free(sb->buf);
+       memset(sb, 0, sizeof(*sb));
+}
+
+void strbuf_reset(struct strbuf *sb) {
+       if (sb->len)
+               strbuf_setlen(sb, 0);
+       sb->eof = 0;
+}
+
+char *strbuf_detach(struct strbuf *sb) {
+       char *res = sb->buf;
        strbuf_init(sb);
+       return res;
+}
+
+void strbuf_grow(struct strbuf *sb, size_t extra) {
+       if (sb->len + extra + 1 <= sb->len)
+               die("you want to use way too much memory");
+       ALLOC_GROW(sb->buf, sb->len + extra + 1, sb->alloc);
+}
+
+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_addf(struct strbuf *sb, const char *fmt, ...) {
+       int len;
+       va_list ap;
+
+       va_start(ap, fmt);
+       len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
+       va_end(ap);
+       if (len < 0) {
+               len = 0;
+       }
+       if (len >= strbuf_avail(sb)) {
+               strbuf_grow(sb, len);
+               va_start(ap, fmt);
+               len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
+               va_end(ap);
+               if (len >= strbuf_avail(sb)) {
+                       die("this should not happen, your snprintf is broken");
+               }
+       }
+       strbuf_setlen(sb, sb->len + len);
 }
 
-static void inline strbuf_add(struct strbuf *sb, int ch) {
-       if (sb->alloc <= sb->len) {
-               sb->alloc = sb->alloc * 3 / 2 + 16;
-               sb->buf = xrealloc(sb->buf, sb->alloc);
+size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f) {
+       size_t res;
+
+       strbuf_grow(sb, size);
+       res = fread(sb->buf + sb->len, 1, size, f);
+       if (res > 0) {
+               strbuf_setlen(sb, sb->len + res);
        }
-       sb->buf[sb->len++] = ch;
+       return res;
 }
 
-static void strbuf_end(struct strbuf *sb) {
-       strbuf_add(sb, 0);
+ssize_t strbuf_read(struct strbuf *sb, int fd)
+{
+       size_t oldlen = sb->len;
+
+       for (;;) {
+               ssize_t cnt;
+
+               strbuf_grow(sb, 8192);
+               cnt = xread(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
+               if (cnt < 0) {
+                       strbuf_setlen(sb, oldlen);
+                       return -1;
+               }
+               if (!cnt)
+                       break;
+               sb->len += cnt;
+       }
+
+       sb->buf[sb->len] = '\0';
+       return sb->len - oldlen;
 }
 
 void read_line(struct strbuf *sb, FILE *fp, int term) {
        int ch;
-       strbuf_begin(sb);
        if (feof(fp)) {
+               strbuf_release(sb);
                sb->eof = 1;
                return;
        }
+
+       strbuf_reset(sb);
        while ((ch = fgetc(fp)) != EOF) {
                if (ch == term)
                        break;
-               strbuf_add(sb, ch);
+               strbuf_grow(sb, 1);
+               sb->buf[sb->len++] = ch;
        }
-       if (ch == EOF && sb->len == 0)
+       if (ch == EOF && sb->len == 0) {
+               strbuf_release(sb);
                sb->eof = 1;
-       strbuf_end(sb);
+       }
+
+       strbuf_grow(sb, 1);
+       sb->buf[sb->len] = '\0';
 }

diff --git a/strbuf.h b/strbuf.h
index 74cc012c2c62d05cb773c6dd4776af0fdc237dfb..b40dc99fd0ac2b052d43bb47401409c7939653fc 100644 (file)
--- a/strbuf.h
+++ b/strbuf.h
@@ -1,13 +1,95 @@
 #ifndef STRBUF_H
 #define STRBUF_H
+
+/*
+ * Strbuf's can be use in many ways: as a byte array, or to store arbitrary
+ * long, overflow safe strings.
+ *
+ * Strbufs has some invariants that are very important to keep in mind:
+ *
+ * 1. the ->buf member is always malloc-ed, hence strbuf's can be used to
+ *    build complex strings/buffers whose final size isn't easily known.
+ *
+ *    It is legal to copy the ->buf pointer away. Though if you want to reuse
+ *    the strbuf after that, setting ->buf to NULL isn't legal.
+ *    `strbuf_detach' is the operation that detachs a buffer from its shell
+ *    while keeping the shell valid wrt its invariants.
+ *
+ * 2. the ->buf member is a byte array that has at least ->len + 1 bytes
+ *    allocated. The extra byte is used to store a '\0', allowing the ->buf
+ *    member to be a valid C-string. Every strbuf function ensure this
+ *    invariant is preserved.
+ *
+ *    Note that it is OK to "play" with the buffer directly if you work it
+ *    that way:
+ *
+ *    strbuf_grow(sb, SOME_SIZE);
+ *    // ... here the memory areay starting at sb->buf, and of length
+ *    // sb_avail(sb) is all yours, and you are sure that sb_avail(sb) is at
+ *    // least SOME_SIZE
+ *    strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
+ *
+ *    Of course, SOME_OTHER_SIZE must be smaller or equal to sb_avail(sb).
+ *
+ *    Doing so is safe, though if it has to be done in many places, adding the
+ *    missing API to the strbuf module is the way to go.
+ *
+ *    XXX: do _not_ assume that the area that is yours is of size ->alloc - 1
+ *         even if it's true in the current implementation. Alloc is somehow a
+ *         "private" member that should not be messed with.
+ */
+
+#include <assert.h>
+
 struct strbuf {
-       int alloc;
-       int len;
+       size_t alloc;
+       size_t len;
        int eof;
        char *buf;
 };
 
+#define STRBUF_INIT  { 0, 0, 0, NULL }
+
+/*----- strbuf life cycle -----*/
 extern void strbuf_init(struct strbuf *);
+extern void strbuf_release(struct strbuf *);
+extern void strbuf_reset(struct strbuf *);
+extern char *strbuf_detach(struct strbuf *);
+
+/*----- strbuf size related -----*/
+static inline size_t strbuf_avail(struct strbuf *sb) {
+    return sb->alloc ? sb->alloc - sb->len - 1 : 0;
+}
+static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
+    assert (len < sb->alloc);
+    sb->len = len;
+    sb->buf[len] = '\0';
+}
+
+extern void strbuf_grow(struct strbuf *, size_t);
+
+/*----- add data in your buffer -----*/
+static inline void strbuf_addch(struct strbuf *sb, int c) {
+       strbuf_grow(sb, 1);
+       sb->buf[sb->len++] = c;
+       sb->buf[sb->len] = '\0';
+}
+
+extern void strbuf_add(struct strbuf *, const void *, size_t);
+static inline void strbuf_addstr(struct strbuf *sb, const char *s) {
+       strbuf_add(sb, s, strlen(s));
+}
+static inline void strbuf_addbuf(struct strbuf *sb, struct strbuf *sb2) {
+       strbuf_add(sb, sb2->buf, sb2->len);
+}
+
+__attribute__((format(printf,2,3)))
+extern void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
+
+extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
+/* XXX: if read fails, any partial read is undone */
+extern ssize_t strbuf_read(struct strbuf *, int fd);
+
 extern void read_line(struct strbuf *, FILE *, int);
 
 #endif /* STRBUF_H */