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apply: document buffer ownership rules across functions

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In general, the private functions in this file were not very
much documented; even though what each of them do is reasonably
self explanatory, the ownership rules for various buffers and
data structures were not very obvious.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano 2012-04-11 14:43:48 -07:00
parent 26693ba81c
commit 92737a2201
1 changed files with 51 additions and 2 deletions
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53
builtin/apply.c
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@ -151,6 +151,10 @@ struct fragment {
unsigned long leading, trailing;
unsigned long oldpos, oldlines;
unsigned long newpos, newlines;
/*
* 'patch' is usually borrowed from buf in apply_patch(),
* but some codepaths store an allocated buffer.
*/
const char *patch;
unsigned free_patch:1,
rejected:1;
@ -332,6 +336,11 @@ static void add_line_info(struct image *img, const char *bol, size_t len, unsign
img->nr++;
}
/*
* "buf" has the file contents to be patched (read from various sources).
* attach it to "image" and add line-based index to it.
* "image" now owns the "buf".
*/
static void prepare_image(struct image *image, char *buf, size_t len,
int prepare_linetable)
{
@ -1607,6 +1616,14 @@ static int parse_fragment(const char *line, unsigned long size,
return offset;
}
/*
* We have seen "diff --git a/... b/..." header (or a traditional patch
* header). Read hunks that belong to this patch into fragments and hang
* them to the given patch structure.
*
* The (fragment->patch, fragment->size) pair points into the memory given
* by the caller, not a copy, when we return.
*/
static int parse_single_patch(const char *line, unsigned long size, struct patch *patch)
{
unsigned long offset = 0;
@ -1700,6 +1717,11 @@ static char *inflate_it(const void *data, unsigned long size,
return out;
}
/*
* Read a binary hunk and return a new fragment; fragment->patch
* points at an allocated memory that the caller must free, so
* it is marked as "->free_patch = 1".
*/
static struct fragment *parse_binary_hunk(char **buf_p,
unsigned long *sz_p,
int *status_p,
@ -1853,6 +1875,13 @@ static int parse_binary(char *buffer, unsigned long size, struct patch *patch)
return used;
}
/*
* Read the patch text in "buffer" taht extends for "size" bytes; stop
* reading after seeing a single patch (i.e. changes to a single file).
* Create fragments (i.e. patch hunks) and hang them to the given patch.
* Return the number of bytes consumed, so that the caller can call us
* again for the next patch.
*/
static int parse_chunk(char *buffer, unsigned long size, struct patch *patch)
{
int hdrsize, patchsize;
@ -2413,6 +2442,11 @@ static void remove_last_line(struct image *img)
img->len -= img->line[--img->nr].len;
}
/*
* The change from "preimage" and "postimage" has been found to
* apply at applied_pos (counts in line numbers) in "img".
* Update "img" to remove "preimage" and replace it with "postimage".
*/
static void update_image(struct image *img,
int applied_pos,
struct image *preimage,
@ -2484,6 +2518,11 @@ static void update_image(struct image *img,
img->nr = nr;
}
/*
* Use the patch-hunk text in "frag" to prepare two images (preimage and
* postimage) for the hunk. Find lines that match "preimage" in "img" and
* replace the part of "img" with "postimage" text.
*/
static int apply_one_fragment(struct image *img, struct fragment *frag,
int inaccurate_eof, unsigned ws_rule,
int nth_fragment)
@ -2774,6 +2813,12 @@ static int apply_binary_fragment(struct image *img, struct patch *patch)
return -1;
}
/*
* Replace "img" with the result of applying the binary patch.
* The binary patch data itself in patch->fragment is still kept
* but the preimage prepared by the caller in "img" is freed here
* or in the helper function apply_binary_fragment() this calls.
*/
static int apply_binary(struct image *img, struct patch *patch)
{
const char *name = patch->old_name ? patch->old_name : patch->new_name;
@ -2981,7 +3026,7 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
return error("patch %s has been renamed/deleted",
patch->old_name);
}
/* We have a patched copy in memory use that */
/* We have a patched copy in memory; use that. */
strbuf_add(&buf, tpatch->result, tpatch->resultsize);
} else if (cached) {
if (read_file_or_gitlink(ce, &buf))
@ -3139,6 +3184,10 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
return 0;
}
/*
* Check and apply the patch in-core; leave the result in patch->result
* for the caller to write it out to the final destination.
*/
static int check_patch(struct patch *patch)
{
struct stat st;
@ -3726,7 +3775,7 @@ static void prefix_patches(struct patch *p)
static int apply_patch(int fd, const char *filename, int options)
{
size_t offset;
struct strbuf buf = STRBUF_INIT;
struct strbuf buf = STRBUF_INIT; /* owns the patch text */
struct patch *list = NULL, **listp = &list;
int skipped_patch = 0;