introduce `git_diff_from_buffer` to parse diffs

Parse diff files into a `git_diff` structure.

6 files changed, 185 insertions, 52 deletions

diff --git a/src/diff.c b/src/diff.c
index c54d3574b..317d49597 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -51,7 +51,7 @@ int git_diff_delta__casecmp(const void *a, const void *b)
 	return val ? val : ((int)da->status - (int)db->status);
 }
 
-static int diff_entry_cmp(const void *a, const void *b)
+int git_diff__entry_cmp(const void *a, const void *b)
 {
 	const git_index_entry *entry_a = a;
 	const git_index_entry *entry_b = b;
@@ -59,7 +59,7 @@ static int diff_entry_cmp(const void *a, const void *b)
 	return strcmp(entry_a->path, entry_b->path);
 }
 
-static int diff_entry_icmp(const void *a, const void *b)
+int git_diff__entry_icmp(const void *a, const void *b)
 {
 	const git_index_entry *entry_a = a;
 	const git_index_entry *entry_b = b;
diff --git a/src/diff.h b/src/diff.h
index 153cd350a..2c0e52ca2 100644
--- a/src/diff.h
+++ b/src/diff.h
@@ -25,6 +25,7 @@
 typedef enum {
 	GIT_DIFF_TYPE_UNKNOWN = 0,
 	GIT_DIFF_TYPE_GENERATED = 1,
+	GIT_DIFF_TYPE_PARSED = 2,
 } git_diff_origin_t;
 
 struct git_diff {
@@ -56,5 +57,8 @@ extern int git_diff_delta__format_file_header(
 extern int git_diff_delta__cmp(const void *a, const void *b);
 extern int git_diff_delta__casecmp(const void *a, const void *b);
 
+extern int git_diff__entry_cmp(const void *a, const void *b);
+extern int git_diff__entry_icmp(const void *a, const void *b);
+
 #endif
 
diff --git a/src/diff_generate.c b/src/diff_generate.c
index 10bc15486..a996bf156 100644
--- a/src/diff_generate.c
+++ b/src/diff_generate.c
@@ -358,22 +358,6 @@ static const char *diff_mnemonic_prefix(
 	return pfx;
 }
 
-static int diff_entry_cmp(const void *a, const void *b)
-{
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
-
-	return strcmp(entry_a->path, entry_b->path);
-}
-
-static int diff_entry_icmp(const void *a, const void *b)
-{
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
-
-	return strcasecmp(entry_a->path, entry_b->path);
-}
-
 void git_diff__set_ignore_case(git_diff *diff, bool ignore_case)
 {
 	if (!ignore_case) {
@@ -382,7 +366,7 @@ void git_diff__set_ignore_case(git_diff *diff, bool ignore_case)
 		diff->strcomp    = git__strcmp;
 		diff->strncomp   = git__strncmp;
 		diff->pfxcomp    = git__prefixcmp;
-		diff->entrycomp  = diff_entry_cmp;
+		diff->entrycomp  = git_diff__entry_cmp;
 
 		git_vector_set_cmp(&diff->deltas, git_diff_delta__cmp);
 	} else {
@@ -391,7 +375,7 @@ void git_diff__set_ignore_case(git_diff *diff, bool ignore_case)
 		diff->strcomp    = git__strcasecmp;
 		diff->strncomp   = git__strncasecmp;
 		diff->pfxcomp    = git__prefixcmp_icase;
-		diff->entrycomp  = diff_entry_icmp;
+		diff->entrycomp  = git_diff__entry_icmp;
 
 		git_vector_set_cmp(&diff->deltas, git_diff_delta__casecmp);
 	}
diff --git a/src/diff_parse.c b/src/diff_parse.c
new file mode 100644
index 000000000..ffdc8df88
--- /dev/null
+++ b/src/diff_parse.c
@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#include "common.h"
+#include "diff.h"
+#include "patch.h"
+#include "patch_parse.h"
+
+typedef struct {
+	struct git_diff base;
+
+	git_vector patches;
+} git_diff_parsed;
+
+static void diff_parsed_free(git_diff *d)
+{
+	git_diff_parsed *diff = (git_diff_parsed *)d;
+	git_patch *patch;
+	size_t i;
+
+	git_vector_foreach(&diff->patches, i, patch)
+		git_patch_free(patch);
+
+	git_vector_free(&diff->patches);
+
+	git_vector_free(&diff->base.deltas);
+	git_pool_clear(&diff->base.pool);
+
+	git__memzero(diff, sizeof(*diff));
+	git__free(diff);
+}
+
+static git_diff_parsed *diff_parsed_alloc(void)
+{
+	git_diff_parsed *diff;
+
+	if ((diff = git__calloc(1, sizeof(git_diff_parsed))) == NULL)
+		return NULL;
+
+	GIT_REFCOUNT_INC(diff);
+	diff->base.type = GIT_DIFF_TYPE_PARSED;
+	diff->base.opts.flags &= ~GIT_DIFF_IGNORE_CASE;
+	diff->base.strcomp = git__strcmp;
+	diff->base.strncomp = git__strncmp;
+	diff->base.pfxcomp = git__prefixcmp;
+	diff->base.entrycomp = git_diff__entry_cmp;
+	diff->base.free_fn = diff_parsed_free;
+
+	git_pool_init(&diff->base.pool, 1);
+
+	if (git_vector_init(&diff->patches, 0, NULL) < 0 ||
+		git_vector_init(&diff->base.deltas, 0, git_diff_delta__cmp) < 0) {
+		git_diff_free(&diff->base);
+		return NULL;
+	}
+
+	git_vector_set_cmp(&diff->base.deltas, git_diff_delta__cmp);
+
+	return diff;
+}
+
+int git_diff_from_buffer(
+	git_diff **out,
+	const char *content,
+	size_t content_len)
+{
+	git_diff_parsed *diff;
+	git_patch *patch;
+	git_patch_parse_ctx *ctx = NULL;
+	int error = 0;
+
+	*out = NULL;
+
+	diff = diff_parsed_alloc();
+	GITERR_CHECK_ALLOC(diff);
+
+	ctx = git_patch_parse_ctx_init(content, content_len, NULL);
+	GITERR_CHECK_ALLOC(ctx);
+
+	while (ctx->remain_len) {
+		if ((error = git_patch_parse(&patch, ctx)) < 0)
+			break;
+
+		git_vector_insert(&diff->patches, patch);
+		git_vector_insert(&diff->base.deltas, patch->delta);
+	}
+
+	if (error == GIT_ENOTFOUND && git_vector_length(&diff->patches) > 0) {
+		giterr_clear();
+		error = 0;
+	}
+
+	git_patch_parse_ctx_free(ctx);
+
+	if (error < 0)
+		git_diff_free(&diff->base);
+	else
+		*out = &diff->base;
+
+	return error;
+}
+
diff --git a/src/patch_parse.c b/src/patch_parse.c
index 991802cb4..ee75663e6 100644
--- a/src/patch_parse.c
+++ b/src/patch_parse.c
@@ -6,27 +6,13 @@
  */
 #include "git2/patch.h"
 #include "patch.h"
+#include "patch_parse.h"
 #include "path.h"
 
 #define parse_err(...) \
 	( giterr_set(GITERR_PATCH, __VA_ARGS__), -1 )
 
 typedef struct {
-	git_refcount rc;
-
-	const char *content;
-	size_t content_len;
-
-	git_patch_options opts;
-
-	const char *line;
-	size_t line_len;
-	size_t line_num;
-
-	size_t remain;
-} git_patch_parse_ctx;
-
-typedef struct {
 	git_patch base;
 
 	git_patch_parse_ctx *ctx;
@@ -60,15 +46,15 @@ GIT_INLINE(bool) parse_ctx_contains(
 static void parse_advance_line(git_patch_parse_ctx *ctx)
 {
 	ctx->line += ctx->line_len;
-	ctx->remain -= ctx->line_len;
-	ctx->line_len = git__linenlen(ctx->line, ctx->remain);
+	ctx->remain_len -= ctx->line_len;
+	ctx->line_len = git__linenlen(ctx->line, ctx->remain_len);
 	ctx->line_num++;
 }
 
 static void parse_advance_chars(git_patch_parse_ctx *ctx, size_t char_cnt)
 {
 	ctx->line += char_cnt;
-	ctx->remain -= char_cnt;
+	ctx->remain_len -= char_cnt;
 	ctx->line_len -= char_cnt;
 }
 
@@ -99,7 +85,7 @@ static int parse_advance_ws(git_patch_parse_ctx *ctx)
 		git__isspace(ctx->line[0])) {
 		ctx->line++;
 		ctx->line_len--;
-		ctx->remain--;
+		ctx->remain_len--;
 		ret = 0;
 	}
 
@@ -413,7 +399,12 @@ static int parse_header_git(
 			ctx->line_num);
 
 	/* Parse remaining header lines */
-	for (parse_advance_line(ctx); ctx->remain > 0; parse_advance_line(ctx)) {
+	for (parse_advance_line(ctx);
+		ctx->remain_len > 0;
+		parse_advance_line(ctx)) {
+
+		bool found = false;
+
 		if (ctx->line_len == 0 || ctx->line[ctx->line_len - 1] != '\n')
 			break;
 
@@ -441,8 +432,14 @@ static int parse_header_git(
 				goto done;
 			}
 
+			found = true;
 			break;
 		}
+		
+		if (!found) {
+			error = parse_err("invalid patch header at line %d", ctx->line_num);
+			goto done;
+		}
 	}
 
 done:
@@ -545,7 +542,7 @@ static int parse_hunk_body(
 	int newlines = hunk->hunk.new_lines;
 
 	for (;
-		ctx->remain > 4 && (oldlines || newlines) &&
+		ctx->remain_len > 4 && (oldlines || newlines) &&
 		memcmp(ctx->line, "@@ -", 4) != 0;
 		parse_advance_line(ctx)) {
 
@@ -590,7 +587,7 @@ static int parse_hunk_body(
 
 		line->content = ctx->line + prefix;
 		line->content_len = ctx->line_len - prefix;
-		line->content_offset = ctx->content_len - ctx->remain;
+		line->content_offset = ctx->content_len - ctx->remain_len;
 		line->origin = origin;
 
 		hunk->line_count++;
@@ -633,7 +630,10 @@ static int parse_patch_header(
 {
 	int error = 0;
 
-	for (ctx->line = ctx->content; ctx->remain > 0; parse_advance_line(ctx)) {
+	for (ctx->line = ctx->remain;
+		ctx->remain_len > 0;
+		parse_advance_line(ctx)) {
+
 		/* This line is too short to be a patch header. */
 		if (ctx->line_len < 6)
 			continue;
@@ -658,7 +658,7 @@ static int parse_patch_header(
 		}
 
 		/* This buffer is too short to contain a patch. */
-		if (ctx->remain < ctx->line_len + 6)
+		if (ctx->remain_len < ctx->line_len + 6)
 			break;
 
 		/* A proper git patch */
@@ -781,6 +781,10 @@ static int parse_patch_binary(
 			&patch->base.binary.old_file, ctx)) < 0)
 		return error;
 
+	if (parse_advance_nl(ctx) < 0)
+		return parse_err("corrupt git binary patch separator at line %d",
+			ctx->line_num);
+
 	patch->base.delta->flags |= GIT_DIFF_FLAG_BINARY;
 	return 0;
 }
@@ -848,7 +852,7 @@ static int check_prefix(
 {
 	const char *path = path_start;
 	size_t prefix_len = patch->ctx->opts.prefix_len;
-	size_t remain = prefix_len;
+	size_t remain_len = prefix_len;
 
 	*out = NULL;
 	*out_len = 0;
@@ -860,14 +864,14 @@ static int check_prefix(
 	while (*path == '/')
 		path++;
 
-	while (*path && remain) {
+	while (*path && remain_len) {
 		if (*path == '/')
-			remain--;
+			remain_len--;
 
 		path++;
 	}
 
-	if (remain || !*path)
+	if (remain_len || !*path)
 		return parse_err(
 			"header filename does not contain %d path components",
 			prefix_len);
@@ -947,7 +951,7 @@ static int check_patch(git_patch_parsed *patch)
 	return 0;
 }
 
-static git_patch_parse_ctx *git_patch_parse_ctx_init(
+git_patch_parse_ctx *git_patch_parse_ctx_init(
 	const char *content,
 	size_t content_len,
 	const git_patch_options *opts)
@@ -966,7 +970,8 @@ static git_patch_parse_ctx *git_patch_parse_ctx_init(
 	}
 
 	ctx->content_len = content_len;
-	ctx->remain = content_len;
+	ctx->remain = ctx->content;
+	ctx->remain_len = ctx->content_len;
 
 	if (opts)
 		memcpy(&ctx->opts, opts, sizeof(git_patch_options));
@@ -986,7 +991,7 @@ static void patch_parse_ctx_free(git_patch_parse_ctx *ctx)
 	git__free(ctx);
 }
 
-static void git_patch_parse_ctx_free(git_patch_parse_ctx *ctx)
+void git_patch_parse_ctx_free(git_patch_parse_ctx *ctx)
 {
 	GIT_REFCOUNT_DEC(ctx, patch_parse_ctx_free);
 }
@@ -1017,11 +1022,12 @@ static void patch_parsed__free(git_patch *p)
 	git__free(patch);
 }
 
-static int git_patch_parse(
+int git_patch_parse(
 	git_patch **out,
 	git_patch_parse_ctx *ctx)
 {
 	git_patch_parsed *patch;
+	size_t start, used;
 	int error = 0;
 
 	assert(out && ctx);
@@ -1042,11 +1048,16 @@ static int git_patch_parse(
 	patch->base.delta->status = GIT_DELTA_MODIFIED;
 	patch->base.delta->nfiles = 2;
 
+	start = ctx->remain_len;
+
 	if ((error = parse_patch_header(patch, ctx)) < 0 ||
 		(error = parse_patch_body(patch, ctx)) < 0 ||
 		(error = check_patch(patch)) < 0)
 		goto done;
 
+	used = start - ctx->remain_len;
+	ctx->remain += used;
+
 	patch->base.diff_opts.old_prefix = patch->old_prefix;
 	patch->base.diff_opts.new_prefix = patch->new_prefix;
 	patch->base.diff_opts.flags |= GIT_DIFF_SHOW_BINARY;
diff --git a/src/patch_parse.h b/src/patch_parse.h
index d5e86073f..da56dad7c 100644
--- a/src/patch_parse.h
+++ b/src/patch_parse.h
@@ -7,6 +7,31 @@
 #ifndef INCLUDE_patch_parse_h__
 #define INCLUDE_patch_parse_h__
 
+typedef struct {
+	git_refcount rc;
+
+	/* Original content buffer */
+	const char *content;
+	size_t content_len;
+
+	git_patch_options opts;
+
+	/* The remaining (unparsed) buffer */
+	const char *remain;
+	size_t remain_len;
+
+	const char *line;
+	size_t line_len;
+	size_t line_num;
+} git_patch_parse_ctx;
+
+extern git_patch_parse_ctx *git_patch_parse_ctx_init(
+	const char *content,
+	size_t content_len,
+	const git_patch_options *opts);
+
+extern void git_patch_parse_ctx_free(git_patch_parse_ctx *ctx);
+
 /**
  * Create a patch for a single file from the contents of a patch buffer.
  *
@@ -22,4 +47,8 @@ extern int git_patch_from_buffer(
 	size_t contents_len,
 	const git_patch_options *opts);
 
+extern int git_patch_parse(
+	git_patch **out,
+	git_patch_parse_ctx *ctx);
+
 #endif