apply: refactor code to drop `line_allocated`
The `struct image` has two members `line` and `line_allocated`. The former member is the one that should be used throughout the code, whereas the latter one is used to track whether the lines have been allocated or not. In practice, the array of lines is always allocated. The reason why we have `line_allocated` is that `remove_first_line()` will advance the array pointer to drop the first entry, and thus it points into the array instead of to the array header. Refactor the function to use memmove(3P) instead, which allows us to get rid of this double bookkeeping. This is less efficient, but I doubt that this matters much in practice. If this judgement call is found to be wrong at a later point in time we can likely refactor the surrounding loop such that we first calculate the number of leading context lines to remove and then remove them in a single call to memmove(3P). Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Patrick Steinhardt committed
Sep 17, 2024 at 12:08 UTC
6eff8b8f406f53ad3301263300016813f1d73c63
1 file changed
+14
-19
apply.c
+14
-19
@@ -281,7 +281,6 @@ struct image {
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size_t len;
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size_t nr;
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size_t alloc;
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- struct line *line_allocated;
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struct line *line;
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};
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#define IMAGE_INIT { 0 }
@@ -295,7 +294,7 @@ static void image_init(struct image *image)
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static void image_clear(struct image *image)
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{
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free(image->buf);
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- free(image->line_allocated);
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+ free(image->line);
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image_init(image);
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}
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@@ -313,10 +312,10 @@ static uint32_t hash_line(const char *cp, size_t len)
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static void image_add_line(struct image *img, const char *bol, size_t len, unsigned flag)
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{
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- ALLOC_GROW(img->line_allocated, img->nr + 1, img->alloc);
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- img->line_allocated[img->nr].len = len;
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- img->line_allocated[img->nr].hash = hash_line(bol, len);
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- img->line_allocated[img->nr].flag = flag;
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+ ALLOC_GROW(img->line, img->nr + 1, img->alloc);
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+ img->line[img->nr].len = len;
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+ img->line[img->nr].hash = hash_line(bol, len);
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+ img->line[img->nr].flag = flag;
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img->nr++;
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}
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@@ -348,15 +347,15 @@ static void image_prepare(struct image *image, char *buf, size_t len,
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image_add_line(image, cp, next - cp, 0);
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cp = next;
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}
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- image->line = image->line_allocated;
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}
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static void image_remove_first_line(struct image *img)
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{
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img->buf += img->line[0].len;
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img->len -= img->line[0].len;
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- img->line++;
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img->nr--;
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+ if (img->nr)
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+ MOVE_ARRAY(img->line, img->line + 1, img->nr);
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}
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static void image_remove_last_line(struct image *img)
@@ -2335,7 +2334,7 @@ static void update_pre_post_images(struct image *preimage,
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: fixed_preimage.nr <= preimage->nr);
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for (i = 0; i < fixed_preimage.nr; i++)
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fixed_preimage.line[i].flag = preimage->line[i].flag;
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- free(preimage->line_allocated);
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+ free(preimage->line);
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*preimage = fixed_preimage;
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/*
@@ -2879,14 +2878,12 @@ static void update_image(struct apply_state *state,
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/* Adjust the line table */
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nr = img->nr + postimage->nr - preimage_limit;
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- if (preimage_limit < postimage->nr) {
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+ if (preimage_limit < postimage->nr)
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/*
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* NOTE: this knows that we never call image_remove_first_line()
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* on anything other than pre/post image.
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*/
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REALLOC_ARRAY(img->line, nr);
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- img->line_allocated = img->line;
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- }
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if (preimage_limit != postimage->nr)
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MOVE_ARRAY(img->line + applied_pos + postimage->nr,
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img->line + applied_pos + preimage_limit,
@@ -3027,8 +3024,8 @@ static int apply_one_fragment(struct apply_state *state,
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newlines.len > 0 && newlines.buf[newlines.len - 1] == '\n') {
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old--;
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strbuf_setlen(&newlines, newlines.len - 1);
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- preimage.line_allocated[preimage.nr - 1].len--;
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- postimage.line_allocated[postimage.nr - 1].len--;
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+ preimage.line[preimage.nr - 1].len--;
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+ postimage.line[postimage.nr - 1].len--;
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}
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leading = frag->leading;
@@ -3062,8 +3059,6 @@ static int apply_one_fragment(struct apply_state *state,
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preimage.len = old - oldlines;
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postimage.buf = newlines.buf;
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postimage.len = newlines.len;
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- preimage.line = preimage.line_allocated;
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- postimage.line = postimage.line_allocated;
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for (;;) {
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@@ -3151,8 +3146,8 @@ static int apply_one_fragment(struct apply_state *state,
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out:
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free(oldlines);
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strbuf_release(&newlines);
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- free(preimage.line_allocated);
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- free(postimage.line_allocated);
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+ free(preimage.line);
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+ free(postimage.line);
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return (applied_pos < 0);
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}
@@ -3752,7 +3747,7 @@ static int apply_data(struct apply_state *state, struct patch *patch,
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patch->result = image.buf;
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patch->resultsize = image.len;
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add_to_fn_table(state, patch);
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- free(image.line_allocated);
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+ free(image.line);
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if (0 < patch->is_delete && patch->resultsize)
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return error(_("removal patch leaves file contents"));