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refactor argv_array into generic code

The submodule code recently grew generic code to build a
dynamic argv array. Many other parts of the code can reuse
this, too, so let's make it generically available.

There are two enhancements not found in the original code:

  1. We now handle the NULL-termination invariant properly,
     even when no strings have been pushed (before, you
     could have an empty, NULL argv). This was not a problem
     for the submodule code, which always pushed at least
     one argument, but was not sufficiently safe for
     generic code.

  2. There is a formatted variant of the "push" function.
     This is a convenience function which was not needed by
     the submodule code, but will make it easier to port
     other users to the new code.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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1 parent 7878b07 commit c1189caeaf726e6c16c8bca7da8bf0b243da478d @peff peff committed with gitster
Showing with 125 additions and 35 deletions.
  1. +46 −0 Documentation/technical/api-argv-array.txt
  2. +2 −0 Makefile
  3. +51 −0 argv-array.c
  4. +20 −0 argv-array.h
  5. +6 −35 submodule.c
View
46 Documentation/technical/api-argv-array.txt
@@ -0,0 +1,46 @@
+argv-array API
+==============
+
+The argv-array API allows one to dynamically build and store
+NULL-terminated lists. An argv-array maintains the invariant that the
+`argv` member always points to a non-NULL array, and that the array is
+always NULL-terminated at the element pointed to by `argv[argc]`. This
+makes the result suitable for passing to functions expecting to receive
+argv from main(), or the link:api-run-command.html[run-command API].
+
+The link:api-string-list.html[string-list API] is similar, but cannot be
+used for these purposes; instead of storing a straight string pointer,
+it contains an item structure with a `util` field that is not compatible
+with the traditional argv interface.
+
+Each `argv_array` manages its own memory. Any strings pushed into the
+array are duplicated, and all memory is freed by argv_array_clear().
+
+Data Structures
+---------------
+
+`struct argv_array`::
+
+ A single array. This should be initialized by assignment from
+ `ARGV_ARRAY_INIT`, or by calling `argv_array_init`. The `argv`
+ member contains the actual array; the `argc` member contains the
+ number of elements in the array, not including the terminating
+ NULL.
+
+Functions
+---------
+
+`argv_array_init`::
+ Initialize an array. This is no different than assigning from
+ `ARGV_ARRAY_INIT`.
+
+`argv_array_push`::
+ Push a copy of a string onto the end of the array.
+
+`argv_array_pushf`::
+ Format a string and push it onto the end of the array. This is a
+ convenience wrapper combining `strbuf_addf` and `argv_array_push`.
+
+`argv_array_clear`::
+ Free all memory associated with the array and return it to the
+ initial, empty state.
View
2 Makefile
@@ -497,6 +497,7 @@ VCSSVN_LIB=vcs-svn/lib.a
LIB_H += advice.h
LIB_H += archive.h
+LIB_H += argv-array.h
LIB_H += attr.h
LIB_H += blob.h
LIB_H += builtin.h
@@ -575,6 +576,7 @@ LIB_OBJS += alloc.o
LIB_OBJS += archive.o
LIB_OBJS += archive-tar.o
LIB_OBJS += archive-zip.o
+LIB_OBJS += argv-array.o
LIB_OBJS += attr.o
LIB_OBJS += base85.o
LIB_OBJS += bisect.o
View
51 argv-array.c
@@ -0,0 +1,51 @@
+#include "cache.h"
+#include "argv-array.h"
+#include "strbuf.h"
+
+static const char *empty_argv_storage = NULL;
+const char **empty_argv = &empty_argv_storage;
+
+void argv_array_init(struct argv_array *array)
+{
+ array->argv = empty_argv;
+ array->argc = 0;
+ array->alloc = 0;
+}
+
+static void argv_array_push_nodup(struct argv_array *array, const char *value)
+{
+ if (array->argv == empty_argv)
+ array->argv = NULL;
+
+ ALLOC_GROW(array->argv, array->argc + 2, array->alloc);
+ array->argv[array->argc++] = value;
+ array->argv[array->argc] = NULL;
+}
+
+void argv_array_push(struct argv_array *array, const char *value)
+{
+ argv_array_push_nodup(array, xstrdup(value));
+}
+
+void argv_array_pushf(struct argv_array *array, const char *fmt, ...)
+{
+ va_list ap;
+ struct strbuf v = STRBUF_INIT;
+
+ va_start(ap, fmt);
+ strbuf_vaddf(&v, fmt, ap);
+ va_end(ap);
+
+ argv_array_push_nodup(array, strbuf_detach(&v, NULL));
+}
+
+void argv_array_clear(struct argv_array *array)
+{
+ if (array->argv != empty_argv) {
+ int i;
+ for (i = 0; i < array->argc; i++)
+ free((char **)array->argv[i]);
+ free(array->argv);
+ }
+ argv_array_init(array);
+}
View
20 argv-array.h
@@ -0,0 +1,20 @@
+#ifndef ARGV_ARRAY_H
+#define ARGV_ARRAY_H
+
+extern const char **empty_argv;
+
+struct argv_array {
+ const char **argv;
+ int argc;
+ int alloc;
+};
+
+#define ARGV_ARRAY_INIT { empty_argv, 0, 0 }
+
+void argv_array_init(struct argv_array *);
+void argv_array_push(struct argv_array *, const char *);
+__attribute__((format (printf,2,3)))
+void argv_array_pushf(struct argv_array *, const char *fmt, ...);
+void argv_array_clear(struct argv_array *);
+
+#endif /* ARGV_ARRAY_H */
View
41 submodule.c
@@ -9,6 +9,7 @@
#include "refs.h"
#include "string-list.h"
#include "sha1-array.h"
+#include "argv-array.h"
static struct string_list config_name_for_path;
static struct string_list config_fetch_recurse_submodules_for_name;
@@ -388,52 +389,22 @@ void check_for_new_submodule_commits(unsigned char new_sha1[20])
sha1_array_append(&ref_tips_after_fetch, new_sha1);
}
-struct argv_array {
- const char **argv;
- unsigned int argc;
- unsigned int alloc;
-};
-
-static void init_argv(struct argv_array *array)
-{
- array->argv = NULL;
- array->argc = 0;
- array->alloc = 0;
-}
-
-static void push_argv(struct argv_array *array, const char *value)
-{
- ALLOC_GROW(array->argv, array->argc + 2, array->alloc);
- array->argv[array->argc++] = xstrdup(value);
- array->argv[array->argc] = NULL;
-}
-
-static void clear_argv(struct argv_array *array)
-{
- int i;
- for (i = 0; i < array->argc; i++)
- free((char **)array->argv[i]);
- free(array->argv);
- init_argv(array);
-}
-
static void add_sha1_to_argv(const unsigned char sha1[20], void *data)
{
- push_argv(data, sha1_to_hex(sha1));
+ argv_array_push(data, sha1_to_hex(sha1));
}
static void calculate_changed_submodule_paths(void)
{
struct rev_info rev;
struct commit *commit;
- struct argv_array argv;
+ struct argv_array argv = ARGV_ARRAY_INIT;
init_revisions(&rev, NULL);
- init_argv(&argv);
- push_argv(&argv, "--"); /* argv[0] program name */
+ argv_array_push(&argv, "--"); /* argv[0] program name */
sha1_array_for_each_unique(&ref_tips_after_fetch,
add_sha1_to_argv, &argv);
- push_argv(&argv, "--not");
+ argv_array_push(&argv, "--not");
sha1_array_for_each_unique(&ref_tips_before_fetch,
add_sha1_to_argv, &argv);
setup_revisions(argv.argc, argv.argv, &rev, NULL);
@@ -460,7 +431,7 @@ static void calculate_changed_submodule_paths(void)
}
}
- clear_argv(&argv);
+ argv_array_clear(&argv);
sha1_array_clear(&ref_tips_before_fetch);
sha1_array_clear(&ref_tips_after_fetch);
initialized_fetch_ref_tips = 0;

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