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The provider chain so far holds the diff-hunks store in front of the terminal builtin computation. Open it to external processes: a pair on a path whose driver configures diff.<driver>.process is answered by a long-running process speaking a pkt-line protocol (following the filter process protocol), registered at the head of the chain and consulted before the store and before any blob is loaded. The protocol starts with the smallest request that can carry an answer: object names alone. A request is the pathname and the pair's old-oid/new-oid, with no content. The process answers with hunk lines, with a zero-hunk success that asserts the blobs equivalent (trailing newlines included), or with status=need-content, on which the pair falls through to the builtin answer. This serves the two shapes that need no content pushed to them: a cache keyed on the blob pair, and a process that fetches the blobs itself (for example over "git cat-file --batch"). A pair whose side is not a stored blob carries a NULL id; the provider sends no request and passes it. Because Git holds no content for the exchange, the answer is used as sent: hunks are validated for order, overlap, lockstep alignment, and magnitude, then replayed without the normalization xdiff applies to diffs it computes itself. The magnitude bound is the blobs' sizes, read from the object database without loading content: a blob of N bytes holds at most N lines. Because the process's answer is authoritative, it outranks the store, and its head-of-chain position says so. A pair the process answers never reaches the store and is never recorded, so nothing it produces enters the store, which holds the builtin answer only. A request it does not answer, whether need-content, a missing capability, or a missing id, passes down the chain to the builtin answer, which is what the store serves, so the store may serve such a pair and a warming run may record it. Entries recorded before a process was configured are not purged; a pair the process answers ignores them, and "git diff-hunks clear" discards them. The provider gates itself per request. The driver is looked up by the old-side path, so a renamed file resolves to the same driver, and by the repository-relative path, so a diff.relative run from a subdirectory names the pair the same way. Options the process is never told about select no process: the whitespace-ignoring options, -I, --anchored, and an algorithm forced by option or configuration (blame routes its algorithm through xdl_opts, so --histogram is covered). The request gains its last field, the path; the consumers change only by filling it, and neither names the process. The provider's state is its repository's pool of running processes, keyed by the configured command, so drivers sharing a command share a process, a submodule speaks to its own, and releasing the provider (from repo_clear()) stops them. The pool owns a copy of each command string, so an entry outlives a config re-read. A command that fails stays as an entry that is not retried: its request and every later one pass, so the store may serve the path for the rest of the command. A protocol error in a response never kills the command. The response is read through a packet reader gentle about framing, so an error takes one path: a single warning, the process stopped and marked failed, and the builtin diff for the rest of the command. That covers garbage bytes, a truncated response, an empty packet, a bare status, and an unrecognized status. Semantically invalid coordinates cost only their pair: the response is drained, the pair is computed, and the process stays alive. A path the protocol cannot carry (an embedded newline, or one too long for a packet) falls back per path rather than costing the command its process. The handshake keeps one fatal check: a process that announces a capability Git did not request aborts the command, as the long-running filter protocol does. Consulting is allowed per command, following the allow_textconv precedent. "git diff", "git log" and "git show", and "git blame" set allow_diff_process; the plumbing diff commands and the interactive-patch machinery never set it, so scripted and staging output stays builtin. The options adjust the flag: - --no-ext-diff clears it and --ext-diff sets it; - --diff-process and --no-diff-process set and clear it alone, leaving external diff drivers as they were; - format-patch clears it unconditionally, so a generated patch applies for recipients without the process; - range-diff passes --no-ext-diff to the "git log" it compares. git blame and the summary formats consult the process. For blame, a pair reported equivalent emits no hunks, so the whole commit passes to its parent. In the stat formats such a pair sums to a zero-count entry, which the "nothing changed" rule omits, as under -w. The subprocess is long-running: one startup cost across a traversal, one round-trip per consulted pair. Answers travel in struct xdl_hunk, new in xdiff-interface.h, holding xdiff's 1-based coordinates; nothing feeds them back to xdiff, since only coordinate consumers consult. A content-carrying request is the natural extension: it would serve sides that are not stored blobs and processes that want content pushed to them, and bring patch output and log -L's range tracking to the same answer. As it stands, a process's answers show in blame and the summary formats while patch output stays builtin. t4080 exercises the protocol, the per-command gate, and the error paths: - each adversarial response shape warns and falls back to builtin, the request log proving which failures disable the process and which keep it alive (a malformed hunk line, coordinates past the blob size, a count overflowing strtol(), overlapping or misaligned hunks, an unrecognized status, a bare status, an empty packet, a mid-response crash, and raw garbage); - a capability-less process and status=abort degrade without noise, and a failed start warns once and returns the path to the store; - a trailing token on a hunk line is ignored, pinning field appendability; - positive consults for git diff, git show, and diff-tree under --ext-diff and --diff-process; textconv output and gitlink sides are never identified; a diff.relative run consults by the repo-relative path; - the equivalence answer is pinned from both consumers, and a warming run past a deferring process records the pair for a later read. Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Michael Montalbo <mmontalbo@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
120 lines
4.4 KiB
C
120 lines
4.4 KiB
C
#ifndef XDIFF_INTERFACE_H
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#define XDIFF_INTERFACE_H
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#include "hash.h"
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#include "xdiff/xdiff.h"
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struct object_database;
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/*
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* Hunk descriptor for externally computed diffs, in xdiff's own
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* coordinates: line numbers are 1-based and a hunk's start is the
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* first line it covers. A caller translates any external "empty side"
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* idiom (such as git diff's start-0/count-0) to a 1-based start before
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* storing hunks in this struct.
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*/
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struct xdl_hunk {
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long old_start, old_count;
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long new_start, new_count;
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};
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/*
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* xdiff isn't equipped to handle content over a gigabyte;
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* we make the cutoff 1GB - 1MB to give some breathing
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* room for constant-sized additions (e.g., merge markers)
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*/
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#define MAX_XDIFF_SIZE (1024UL * 1024 * 1023)
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/**
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* The `xdiff_emit_line_fn` function can return 1 to abort early, or 0
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* to continue processing. Note that doing so is an all-or-nothing
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* affair, as returning 1 will return all the way to the top-level,
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* e.g. the xdi_diff_outf() call to generate the diff.
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*
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* Thus returning 1 means you won't be getting any more diff lines. If
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* you need something in-between those two options you'll to use
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* `xdl_emit_hunk_consume_func_t` and implement your own version of
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* xdl_emit_diff().
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*
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* We may extend the interface in the future to understand other more
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* granular return values. While you should return 1 to exit early,
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* doing so will currently make your early return indistinguishable
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* from an error internal to xdiff, xdiff itself will see that
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* non-zero return and translate it to -1.
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*
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* See "diff_grep" in diffcore-pickaxe.c and "quick_consume" in diff.c
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* for a trick to work around this, i.e. using the "consume_callback_data"
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* to note the desired early return.
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*/
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typedef int (*xdiff_emit_line_fn)(void *, char *, unsigned long);
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typedef void (*xdiff_emit_hunk_fn)(void *data,
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long old_begin, long old_nr,
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long new_begin, long new_nr,
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const char *func, long funclen);
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int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *ecb);
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int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
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xdiff_emit_hunk_fn hunk_fn,
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xdiff_emit_line_fn line_fn,
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void *consume_callback_data,
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xpparam_t const *xpp, xdemitconf_t const *xecfg);
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struct range_set;
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/*
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* Like xdi_diff_outf(), but forwards only the lines within the given
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* (post-image) line ranges to line_fn, as "git log -L" scopes its output.
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* Returns line_fn's latched return value (so a consumer can signal a hit
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* with a non-zero return), or non-zero on xdiff failure. Defined in
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* diff.c (it reuses the line-range filter there).
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*/
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int diff_emit_line_ranges(mmfile_t *mf1, mmfile_t *mf2,
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const struct range_set *ranges,
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xdiff_emit_line_fn line_fn, void *cb_data,
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xpparam_t *xpp, xdemitconf_t *xecfg);
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int read_mmfile(mmfile_t *ptr, const char *filename);
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void read_mmblob(mmfile_t *ptr, struct object_database *odb,
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const struct object_id *oid);
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int buffer_is_binary(const char *ptr, unsigned long size);
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void xdiff_set_find_func(xdemitconf_t *xecfg, const char *line, int cflags);
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void xdiff_clear_find_func(xdemitconf_t *xecfg);
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struct config_context;
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int parse_conflict_style_name(const char *value);
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const char *conflict_style_name(int style);
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int git_xmerge_config(const char *var, const char *value,
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const struct config_context *ctx, void *cb);
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extern int git_xmerge_style;
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/*
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* Compare the strings l1 with l2 which are of size s1 and s2 respectively.
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* Returns 1 if the strings are deemed equal, 0 otherwise.
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* The `flags` given as XDF_WHITESPACE_FLAGS determine how white spaces
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* are treated for the comparison.
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*/
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int xdiff_compare_lines(const char *l1, long s1,
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const char *l2, long s2, long flags);
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/*
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* Returns a hash of the string s of length len.
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* The `flags` given as XDF_WHITESPACE_FLAGS determine how white spaces
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* are treated for the hash.
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*/
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unsigned long xdiff_hash_string(const char *s, size_t len, long flags);
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struct strbuf;
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/*
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* Append a unified-diff hunk header to `out`, e.g.
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* "@@ -<old> +<new> @@ func\n". The header comes from wrapping xdiff's
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* own hunk-header emitter, so it matches what a normal diff would
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* produce for these begins and counts. For a side with no lines
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* (count 0) the begin is the line before the change, and a count of 1
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* is omitted.
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*/
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void xdiff_emit_hunk_header(struct strbuf *out,
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long old_begin, long old_count,
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long new_begin, long new_count,
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const char *func, long funclen);
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#endif
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