Rewrite convert_to_{git,working_tree} to use strbuf's.

* Now, those functions take an "out" strbuf argument, where they store their
  result if any. In that case, it also returns 1, else it returns 0.
* those functions support "in place" editing, in the sense that it's OK to
  call them this way:
    convert_to_git(path, sb->buf, sb->len, sb);
  When doable, conversions are done in place for real, else the strbuf
  content is just replaced with the new one, transparentely for the caller.

If you want to create a new filter working this way, being the accumulation
of filter1, filter2, ... filtern, then your meta_filter would be:

    int meta_filter(..., const char *src, size_t len, struct strbuf *sb)
    {
        int ret = 0;
        ret |= filter1(...., src, len, sb);
        if (ret) {
            src = sb->buf;
            len = sb->len;
        }
        ret |= filter2(...., src, len, sb);
        if (ret) {
            src = sb->buf;
            len = sb->len;
        }
        ....
        return ret | filtern(..., src, len, sb);
    }

That's why subfilters the convert_to_* functions called were also rewritten
to work this way.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-apply.c

@@ -1446,8 +1446,7 @@ static int read_old_data(struct stat *st, const char *path, char **buf_p, unsign
 {
 	int fd;
 	unsigned long got;
-	unsigned long nsize;
-	char *nbuf;
+	struct strbuf nbuf;
 	unsigned long size = *size_p;
 	char *buf = *buf_p;
 
@@ -1466,13 +1465,12 @@ static int read_old_data(struct stat *st, const char *path, char **buf_p, unsign
 			got += ret;
 		}
 		close(fd);
-		nsize = got;
-		nbuf = convert_to_git(path, buf, &nsize);
-		if (nbuf) {
+		strbuf_init(&nbuf, 0);
+		if (convert_to_git(path, buf, size, &nbuf)) {
 			free(buf);
-			*buf_p = nbuf;
-			*alloc_p = nsize;
-			*size_p = nsize;
+			*buf_p = nbuf.buf;
+			*alloc_p = nbuf.alloc;
+			*size_p = nbuf.len;
 		}
 		return got != size;
 	default:
@@ -2439,7 +2437,7 @@ static void add_index_file(const char *path, unsigned mode, void *buf, unsigned
 static int try_create_file(const char *path, unsigned int mode, const char *buf, unsigned long size)
 {
 	int fd;
-	char *nbuf;
+	struct strbuf nbuf;
 
 	if (S_ISGITLINK(mode)) {
 		struct stat st;
@@ -2458,9 +2456,11 @@ static int try_create_file(const char *path, unsigned int mode, const char *buf,
 	if (fd < 0)
 		return -1;
 
-	nbuf = convert_to_working_tree(path, buf, &size);
-	if (nbuf)
-		buf = nbuf;
+	strbuf_init(&nbuf, 0);
+	if (convert_to_working_tree(path, buf, size, &nbuf)) {
+		size = nbuf.len;
+		buf  = nbuf.buf;
+	}
 
 	while (size) {
 		int written = xwrite(fd, buf, size);
@@ -2473,8 +2473,7 @@ static int try_create_file(const char *path, unsigned int mode, const char *buf,
 	}
 	if (close(fd) < 0)
 		die("closing file %s: %s", path, strerror(errno));
-	if (nbuf)
-		free(nbuf);
+	strbuf_release(&nbuf);
 	return 0;
 }
 

builtin-archive.c

@@ -81,22 +81,21 @@ static int run_remote_archiver(const char *remote, int argc,
 	return !!rv;
 }
 
-static void *format_subst(const struct commit *commit, const char *format,
-                          unsigned long *sizep)
+static void format_subst(const struct commit *commit,
+                         const char *src, size_t len,
+                         struct strbuf *buf)
 {
-	unsigned long len = *sizep;
-	const char *a = format;
-	struct strbuf result;
+	char *to_free = NULL;
 	struct strbuf fmt;
 
-	strbuf_init(&result, 0);
+	if (src == buf->buf)
+		to_free = strbuf_detach(buf);
 	strbuf_init(&fmt, 0);
-
 	for (;;) {
 		const char *b, *c;
 
-		b = memmem(a, len, "$Format:", 8);
-		if (!b || a + len < b + 9)
+		b = memmem(src, len, "$Format:", 8);
+		if (!b || src + len < b + 9)
 			break;
 		c = memchr(b + 8, '$', len - 8);
 		if (!c)
@@ -105,62 +104,57 @@ static void *format_subst(const struct commit *commit, const char *format,
 		strbuf_reset(&fmt);
 		strbuf_add(&fmt, b + 8, c - b - 8);
 
-		strbuf_add(&result, a, b - a);
-		format_commit_message(commit, fmt.buf, &result);
-		len -= c + 1 - a;
-		a = c + 1;
+		strbuf_add(buf, src, b - src);
+		format_commit_message(commit, fmt.buf, buf);
+		len -= c + 1 - src;
+		src  = c + 1;
 	}
-
-	strbuf_add(&result, a, len);
-
-	*sizep = result.len;
-
+	strbuf_add(buf, src, len);
 	strbuf_release(&fmt);
-	return strbuf_detach(&result);
+	free(to_free);
 }
 
-static void *convert_to_archive(const char *path,
-                                const void *src, unsigned long *sizep,
-                                const struct commit *commit)
+static int convert_to_archive(const char *path,
+                              const void *src, size_t len,
+                              struct strbuf *buf,
+                              const struct commit *commit)
 {
 	static struct git_attr *attr_export_subst;
 	struct git_attr_check check[1];
 
 	if (!commit)
-		return NULL;
+		return 0;
 
-        if (!attr_export_subst)
-                attr_export_subst = git_attr("export-subst", 12);
+	if (!attr_export_subst)
+		attr_export_subst = git_attr("export-subst", 12);
 
 	check[0].attr = attr_export_subst;
 	if (git_checkattr(path, ARRAY_SIZE(check), check))
-		return NULL;
+		return 0;
 	if (!ATTR_TRUE(check[0].value))
-		return NULL;
+		return 0;
 
-	return format_subst(commit, src, sizep);
+	format_subst(commit, src, len, buf);
+	return 1;
 }
 
 void *sha1_file_to_archive(const char *path, const unsigned char *sha1,
                            unsigned int mode, enum object_type *type,
-                           unsigned long *size,
+                           unsigned long *sizep,
                            const struct commit *commit)
 {
-	void *buffer, *converted;
+	void *buffer;
 
-	buffer = read_sha1_file(sha1, type, size);
+	buffer = read_sha1_file(sha1, type, sizep);
 	if (buffer && S_ISREG(mode)) {
-		converted = convert_to_working_tree(path, buffer, size);
-		if (converted) {
-			free(buffer);
-			buffer = converted;
-		}
-
-		converted = convert_to_archive(path, buffer, size, commit);
-		if (converted) {
-			free(buffer);
-			buffer = converted;
-		}
+		struct strbuf buf;
+
+		strbuf_init(&buf, 0);
+		strbuf_attach(&buf, buffer, *sizep, *sizep + 1);
+		convert_to_working_tree(path, buf.buf, buf.len, &buf);
+		convert_to_archive(path, buf.buf, buf.len, &buf, commit);
+		*sizep = buf.len;
+		buffer = buf.buf;
 	}
 
 	return buffer;

cache.h

@@ -2,6 +2,7 @@
 #define CACHE_H
 
 #include "git-compat-util.h"
+#include "strbuf.h"
 
 #include SHA1_HEADER
 #include <zlib.h>
@@ -589,8 +590,9 @@ extern void trace_printf(const char *format, ...);
 extern void trace_argv_printf(const char **argv, int count, const char *format, ...);
 
 /* convert.c */
-extern char *convert_to_git(const char *path, const char *src, unsigned long *sizep);
-extern char *convert_to_working_tree(const char *path, const char *src, unsigned long *sizep);
+/* returns 1 if *dst was used */
+extern int convert_to_git(const char *path, const char *src, size_t len, struct strbuf *dst);
+extern int convert_to_working_tree(const char *path, const char *src, size_t len, struct strbuf *dst);
 
 /* diff.c */
 extern int diff_auto_refresh_index;