Extract common example helpers and reorg examples

This reorganizes a few of the examples so that the main function
comes first with the argument parsing extracted into a helper
that can come at the end of the file (so the example focuses more
on the use of libgit2 instead of command line support).  This also
creates a shared examples/common.[ch] so that useful helper funcs
can be shared across examples instead of repeated.

examples/CMakeLists.txt

@@ -9,6 +9,8 @@ ENDIF()
 FILE(GLOB SRC_EXAMPLE_APPS RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} *.c)
 FOREACH(src_app ${SRC_EXAMPLE_APPS})
 	STRING(REPLACE ".c" "" app_name ${src_app})
-	ADD_EXECUTABLE(${app_name} ${src_app})
-	TARGET_LINK_LIBRARIES(${app_name} git2)
+	IF(NOT ${app_name} STREQUAL "common")
+		ADD_EXECUTABLE(${app_name} ${src_app} "common.c")
+		TARGET_LINK_LIBRARIES(${app_name} git2)
+	ENDIF()
 ENDFOREACH()

examples/Makefile

@@ -8,7 +8,7 @@ APPS = general showindex diff rev-list cat-file status log rev-parse init
 all: $(APPS)
 
 % : %.c
-	$(CC) -o $@ $(CFLAGS) $< $(LFLAGS)
+	$(CC) -o $@ common.c $(CFLAGS) $< $(LFLAGS)
 
 clean:
 	$(RM) $(APPS)

examples/common.c

+/*
+ * 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"
+
+void check_lg2(int error, const char *message, const char *extra)
+{
+	const git_error *lg2err;
+	const char *lg2msg = "", *lg2spacer = "";
+
+	if (!error)
+		return;
+
+	if ((lg2err = giterr_last()) != NULL && lg2err->message != NULL) {
+		lg2msg = lg2err->message;
+		lg2spacer = " - ";
+	}
+
+	if (extra)
+		fprintf(stderr, "%s '%s' [%d]%s%s\n",
+			message, extra, error, lg2spacer, lg2msg);
+	else
+		fprintf(stderr, "%s [%d]%s%s\n",
+			message, error, lg2spacer, lg2msg);
+
+	exit(1);
+}
+
+void fatal(const char *message, const char *extra)
+{
+	if (extra)
+		fprintf(stderr, "%s %s\n", message, extra);
+	else
+		fprintf(stderr, "%s\n", message);
+
+	exit(1);
+}
+
+size_t is_prefixed(const char *str, const char *pfx)
+{
+	size_t len = strlen(pfx);
+	return strncmp(str, pfx, len) ? 0 : len;
+}
+
+int match_str_arg(
+	const char **out, struct args_info *args, const char *opt)
+{
+	const char *found = args->argv[args->pos];
+	size_t len = is_prefixed(found, opt);
+
+	if (!len)
+		return 0;
+
+	if (!found[len]) {
+		if (args->pos + 1 == args->argc)
+			fatal("expected value following argument", opt);
+		args->pos += 1;
+		*out = args->argv[args->pos];
+		return 1;
+	}
+
+	if (found[len] == '=') {
+		*out = found + len + 1;
+		return 1;
+	}
+
+	return 0;
+}
+
+static const char *match_numeric_arg(struct args_info *args, const char *opt)
+{
+	const char *found = args->argv[args->pos];
+	size_t len = is_prefixed(found, opt);
+
+	if (!len)
+		return NULL;
+
+	if (!found[len]) {
+		if (args->pos + 1 == args->argc)
+			fatal("expected numeric value following argument", opt);
+		args->pos += 1;
+		found = args->argv[args->pos];
+	} else {
+		found = found + len;
+		if (*found == '=')
+			found++;
+	}
+
+	return found;
+}
+
+int match_uint16_arg(
+	uint16_t *out, struct args_info *args, const char *opt)
+{
+	const char *found = match_numeric_arg(args, opt);
+	uint16_t val;
+	char *endptr = NULL;
+
+	if (!found)
+		return 0;
+
+	val = (uint16_t)strtoul(found, &endptr, 0);
+	if (!endptr || *endptr != '\0')
+		fatal("expected number after argument", opt);
+
+	if (out)
+		*out = val;
+	return 1;
+}
+
+static int match_int_internal(
+	int *out, const char *str, int allow_negative, const char *opt)
+{
+	char *endptr = NULL;
+	int	  val = (int)strtol(str, &endptr, 10);
+
+	if (!endptr || *endptr != '\0')
+		fatal("expected number", opt);
+	else if (val < 0 && !allow_negative)
+		fatal("negative values are not allowed", opt);
+
+	if (out)
+		*out = val;
+
+	return 1;
+}
+
+int is_integer(int *out, const char *str, int allow_negative)
+{
+	return match_int_internal(out, str, allow_negative, NULL);
+}
+
+int match_int_arg(
+	int *out, struct args_info *args, const char *opt, int allow_negative)
+{
+	const char *found = match_numeric_arg(args, opt);
+	if (!found)
+		return 0;
+	return match_int_internal(out, found, allow_negative, opt);
+}
+
+int diff_output(
+	const git_diff_delta *d,
+	const git_diff_hunk *h,
+	const git_diff_line *l,
+	void *p)
+{
+	FILE *fp = p;
+
+	(void)d; (void)h;
+
+	if (!fp)
+		fp = stdout;
+
+	if (l->origin == GIT_DIFF_LINE_CONTEXT ||
+		l->origin == GIT_DIFF_LINE_ADDITION ||
+		l->origin == GIT_DIFF_LINE_DELETION)
+		fputc(l->origin, fp);
+
+	fwrite(l->content, 1, l->content_len, fp);
+
+	return 0;
+}
+
+void treeish_to_tree(
+	git_tree **out, git_repository *repo, const char *treeish)
+{
+	git_object *obj = NULL;
+
+	check_lg2(
+		git_revparse_single(&obj, repo, treeish),
+		"looking up object", treeish);
+
+	check_lg2(
+		git_object_peel((git_object **)out, obj, GIT_OBJ_TREE),
+		"resolving object to tree", treeish);
+
+	git_object_free(obj);
+}
+

examples/common.h

+/*
+ * 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 <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <git2.h>
+
+/**
+ * Check libgit2 error code, printing error to stderr on failure and
+ * exiting the program.
+ */
+extern void check_lg2(int error, const char *message, const char *extra);
+
+/**
+ * Exit the program, printing error to stderr
+ */
+extern void fatal(const char *message, const char *extra);
+
+/**
+ * Check if a string has the given prefix.  Returns 0 if not prefixed
+ * or the length of the prefix if it is.
+ */
+extern size_t is_prefixed(const char *str, const char *pfx);
+
+/**
+ * Match an integer string, returning 1 if matched, 0 if not.
+ */
+extern int is_integer(int *out, const char *str, int allow_negative);
+
+struct args_info {
+	int    argc;
+	char **argv;
+	int    pos;
+};
+#define ARGS_INFO_INIT { argc, argv, 0 }
+
+/**
+ * Check current `args` entry against `opt` string.  If it matches
+ * exactly, take the next arg as a string; if it matches as a prefix with
+ * an equal sign, take the remainder as a string; otherwise return 0.
+ */
+extern int match_str_arg(
+	const char **out, struct args_info *args, const char *opt);
+
+/**
+ * Check current `args` entry against `opt` string parsing as uint16.  If
+ * `opt` matches exactly, take the next arg as a uint16_t value; if `opt`
+ * is a prefix (equal sign optional), take the remainder of the arg as a
+ * uint16_t value; otherwise return 0.
+ */
+extern int match_uint16_arg(
+	uint16_t *out, struct args_info *args, const char *opt);
+
+/**
+ * Check current `args` entry against `opt` string parsing as int.  If
+ * `opt` matches exactly, take the next arg as an int value; if it matches
+ * as a prefix (equal sign optional), take the remainder of the arg as a
+ * int value; otherwise return 0.
+ */
+extern int match_int_arg(
+	int *out, struct args_info *args, const char *opt, int allow_negative);
+
+/**
+ * Basic output function for plain text diff output
+ * Pass `FILE*` such as `stdout` or `stderr` as payload (or NULL == `stdout`)
+ */
+extern int diff_output(
+	const git_diff_delta*, const git_diff_hunk*, const git_diff_line*, void*);
+
+/**
+ * Convert a treeish argument to an actual tree; this will call check_lg2
+ * and exit the program if `treeish` cannot be resolved to a tree
+ */
+extern void treeish_to_tree(
+	git_tree **out, git_repository *repo, const char *treeish);

examples/status.c

@@ -4,18 +4,8 @@
  * 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 <git2.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
 
-enum {
-	FORMAT_DEFAULT   = 0,
-	FORMAT_LONG      = 1,
-	FORMAT_SHORT     = 2,
-	FORMAT_PORCELAIN = 3,
-};
-#define MAX_PATHSPEC 8
+#include "common.h"
 
 /*
  * This example demonstrates the use of the libgit2 status APIs,
@@ -35,32 +25,83 @@ enum {
  * - A sample status formatter that matches the "short" format
  */
 
-static void check(int error, const char *message, const char *extra)
+enum {
+	FORMAT_DEFAULT   = 0,
+	FORMAT_LONG      = 1,
+	FORMAT_SHORT     = 2,
+	FORMAT_PORCELAIN = 3,
+};
+
+#define MAX_PATHSPEC 8
+
+struct opts {
+    git_status_options statusopt;
+    char *repodir;
+    char *pathspec[MAX_PATHSPEC];
+    int npaths;
+    int format;
+    int zterm;
+    int showbranch;
+};
+
+static void parse_opts(struct opts *o, int argc, char *argv[]);
+static void show_branch(git_repository *repo, int format);
+static void print_long(git_repository *repo, git_status_list *status);
+static void print_short(git_repository *repo, git_status_list *status);
+
+int main(int argc, char *argv[])
 {
-	const git_error *lg2err;
-	const char *lg2msg = "", *lg2spacer = "";
+	git_repository *repo = NULL;
+	git_status_list *status;
+	struct opts o = { GIT_STATUS_OPTIONS_INIT, "." };
 
-	if (!error)
-		return;
+	git_threads_init();
 
-	if ((lg2err = giterr_last()) != NULL && lg2err->message != NULL) {
-		lg2msg = lg2err->message;
-		lg2spacer = " - ";
-	}
+	o.statusopt.show  = GIT_STATUS_SHOW_INDEX_AND_WORKDIR;
+	o.statusopt.flags = GIT_STATUS_OPT_INCLUDE_UNTRACKED |
+		GIT_STATUS_OPT_RENAMES_HEAD_TO_INDEX |
+		GIT_STATUS_OPT_SORT_CASE_SENSITIVELY;
+
+	parse_opts(&o, argc, argv);
+
+	/*
+	 * Try to open the repository at the given path (or at the current
+	 * directory if none was given).
+	 */
+	check_lg2(git_repository_open_ext(&repo, o.repodir, 0, NULL),
+		  "Could not open repository", o.repodir);
+
+	if (git_repository_is_bare(repo))
+		fatal("Cannot report status on bare repository",
+			git_repository_path(repo));
+
+	/*
+	 * Run status on the repository
+	 *
+	 * Because we want to simluate a full "git status" run and want to
+	 * support some command line options, we use `git_status_foreach_ext()`
+	 * instead of just the plain status call.  This allows (a) iterating
+	 * over the index and then the workdir and (b) extra flags that control
+	 * which files are included.  If you just want simple status (e.g. to
+	 * enumerate files that are modified) then you probably don't need the
+	 * extended API.
+	 */
+	check_lg2(git_status_list_new(&status, repo, &o.statusopt),
+		  "Could not get status", NULL);
 
-	if (extra)
-		fprintf(stderr, "%s '%s' [%d]%s%s\n",
-			message, extra, error, lg2spacer, lg2msg);
+	if (o.showbranch)
+		show_branch(repo, o.format);
+
+	if (o.format == FORMAT_LONG)
+		print_long(repo, status);
 	else
-		fprintf(stderr, "%s [%d]%s%s\n",
-			message, error, lg2spacer, lg2msg);
+		print_short(repo, status);
 
-	exit(1);
-}
+	git_status_list_free(status);
+	git_repository_free(repo);
+	git_threads_shutdown();
 
-static void fail(const char *message)
-{
-	check(-1, message, NULL);
+	return 0;
 }
 
 static void show_branch(git_repository *repo, int format)
@@ -78,7 +119,7 @@ static void show_branch(git_repository *repo, int format)
 		if (!strncmp(branch, "refs/heads/", strlen("refs/heads/")))
 			branch += strlen("refs/heads/");
 	} else
-		check(error, "failed to get current branch", NULL);
+		check_lg2(error, "failed to get current branch", NULL);
 
 	if (format == FORMAT_LONG)
 		printf("# On branch %s\n",
@@ -341,103 +382,58 @@ static void print_short(git_repository *repo, git_status_list *status)
 	}
 }
 
-int main(int argc, char *argv[])
+static void parse_opts(struct opts *o, int argc, char *argv[])
 {
-	git_repository *repo = NULL;
-	int i, npaths = 0, format = FORMAT_DEFAULT, zterm = 0, showbranch = 0;
-	git_status_options opt = GIT_STATUS_OPTIONS_INIT;
-	git_status_list *status;
-	char *repodir = ".", *pathspec[MAX_PATHSPEC];
+	struct args_info args = ARGS_INFO_INIT;
 
-	opt.show  = GIT_STATUS_SHOW_INDEX_AND_WORKDIR;
-	opt.flags = GIT_STATUS_OPT_INCLUDE_UNTRACKED |
-		GIT_STATUS_OPT_RENAMES_HEAD_TO_INDEX |
-		GIT_STATUS_OPT_SORT_CASE_SENSITIVELY;
+	for (args.pos = 1; args.pos < argc; ++args.pos) {
+		char *a = argv[args.pos];
 
-	for (i = 1; i < argc; ++i) {
-		if (argv[i][0] != '-') {
-			if (npaths < MAX_PATHSPEC)
-				pathspec[npaths++] = argv[i];
+		if (a[0] != '-') {
+			if (o->npaths < MAX_PATHSPEC)
+				o->pathspec[o->npaths++] = a;
 			else
-				fail("Example only supports a limited pathspec");
+				fatal("Example only supports a limited pathspec", NULL);
 		}
-		else if (!strcmp(argv[i], "-s") || !strcmp(argv[i], "--short"))
-			format = FORMAT_SHORT;
-		else if (!strcmp(argv[i], "--long"))
-			format = FORMAT_LONG;
-		else if (!strcmp(argv[i], "--porcelain"))
-			format = FORMAT_PORCELAIN;
-		else if (!strcmp(argv[i], "-b") || !strcmp(argv[i], "--branch"))
-			showbranch = 1;
-		else if (!strcmp(argv[i], "-z")) {
-			zterm = 1;
-			if (format == FORMAT_DEFAULT)
-				format = FORMAT_PORCELAIN;
+		else if (!strcmp(a, "-s") || !strcmp(a, "--short"))
+			o->format = FORMAT_SHORT;
+		else if (!strcmp(a, "--long"))
+			o->format = FORMAT_LONG;
+		else if (!strcmp(a, "--porcelain"))
+			o->format = FORMAT_PORCELAIN;
+		else if (!strcmp(a, "-b") || !strcmp(a, "--branch"))
+			o->showbranch = 1;
+		else if (!strcmp(a, "-z")) {
+			o->zterm = 1;
+			if (o->format == FORMAT_DEFAULT)
+				o->format = FORMAT_PORCELAIN;
 		}
-		else if (!strcmp(argv[i], "--ignored"))
-			opt.flags |= GIT_STATUS_OPT_INCLUDE_IGNORED;
-		else if (!strcmp(argv[i], "-uno") ||
-				 !strcmp(argv[i], "--untracked-files=no"))
-			opt.flags &= ~GIT_STATUS_OPT_INCLUDE_UNTRACKED;
-		else if (!strcmp(argv[i], "-unormal") ||
-				 !strcmp(argv[i], "--untracked-files=normal"))
-			opt.flags |= GIT_STATUS_OPT_INCLUDE_UNTRACKED;
-		else if (!strcmp(argv[i], "-uall") ||
-				 !strcmp(argv[i], "--untracked-files=all"))
-			opt.flags |= GIT_STATUS_OPT_INCLUDE_UNTRACKED |
+		else if (!strcmp(a, "--ignored"))
+			o->statusopt.flags |= GIT_STATUS_OPT_INCLUDE_IGNORED;
+		else if (!strcmp(a, "-uno") ||
+				 !strcmp(a, "--untracked-files=no"))
+			o->statusopt.flags &= ~GIT_STATUS_OPT_INCLUDE_UNTRACKED;
+		else if (!strcmp(a, "-unormal") ||
+				 !strcmp(a, "--untracked-files=normal"))
+			o->statusopt.flags |= GIT_STATUS_OPT_INCLUDE_UNTRACKED;
+		else if (!strcmp(a, "-uall") ||
+				 !strcmp(a, "--untracked-files=all"))
+			o->statusopt.flags |= GIT_STATUS_OPT_INCLUDE_UNTRACKED |
 				GIT_STATUS_OPT_RECURSE_UNTRACKED_DIRS;
-		else if (!strcmp(argv[i], "--ignore-submodules=all"))
-			opt.flags |= GIT_STATUS_OPT_EXCLUDE_SUBMODULES;
-		else if (!strncmp(argv[i], "--git-dir=", strlen("--git-dir=")))
-			repodir = argv[i] + strlen("--git-dir=");
+		else if (!strcmp(a, "--ignore-submodules=all"))
+			o->statusopt.flags |= GIT_STATUS_OPT_EXCLUDE_SUBMODULES;
+		else if (!strncmp(a, "--git-dir=", strlen("--git-dir=")))
+			o->repodir = a + strlen("--git-dir=");
 		else
-			check(-1, "Unsupported option", argv[i]);
+			check_lg2(-1, "Unsupported option", a);
 	}
 
-	if (format == FORMAT_DEFAULT)
-		format = FORMAT_LONG;
-	if (format == FORMAT_LONG)
-		showbranch = 1;
-	if (npaths > 0) {
-		opt.pathspec.strings = pathspec;
-		opt.pathspec.count   = npaths;
+	if (o->format == FORMAT_DEFAULT)
+		o->format = FORMAT_LONG;
+	if (o->format == FORMAT_LONG)
+		o->showbranch = 1;
+	if (o->npaths > 0) {
+		o->statusopt.pathspec.strings = o->pathspec;
+		o->statusopt.pathspec.count   = o->npaths;
 	}
-
-	/*
-	 * Try to open the repository at the given path (or at the current
-	 * directory if none was given).
-	 */
-	check(git_repository_open_ext(&repo, repodir, 0, NULL),
-		  "Could not open repository", repodir);
-
-	if (git_repository_is_bare(repo))
-		fail("Cannot report status on bare repository");
-
-	/*
-	 * Run status on the repository
-	 *
-	 * Because we want to simluate a full "git status" run and want to
-	 * support some command line options, we use `git_status_foreach_ext()`
-	 * instead of just the plain status call.  This allows (a) iterating
-	 * over the index and then the workdir and (b) extra flags that control
-	 * which files are included.  If you just want simple status (e.g. to
-	 * enumerate files that are modified) then you probably don't need the
-	 * extended API.
-	 */
-	check(git_status_list_new(&status, repo, &opt),
-		  "Could not get status", NULL);
-
-	if (showbranch)
-		show_branch(repo, format);
-
-	if (format == FORMAT_LONG)
-		print_long(repo, status);
-	else
-		print_short(repo, status);
-
-	git_status_list_free(status);
-	git_repository_free(repo);
-
-	return 0;
 }
-