reftable: utility functions

This commit provides basic utility classes for the reftable library.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

reftable/basics.c

@@ -0,0 +1,128 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "basics.h"
+
+void put_be24(uint8_t *out, uint32_t i)
+{
+	out[0] = (uint8_t)((i >> 16) & 0xff);
+	out[1] = (uint8_t)((i >> 8) & 0xff);
+	out[2] = (uint8_t)(i & 0xff);
+}
+
+uint32_t get_be24(uint8_t *in)
+{
+	return (uint32_t)(in[0]) << 16 | (uint32_t)(in[1]) << 8 |
+	       (uint32_t)(in[2]);
+}
+
+void put_be16(uint8_t *out, uint16_t i)
+{
+	out[0] = (uint8_t)((i >> 8) & 0xff);
+	out[1] = (uint8_t)(i & 0xff);
+}
+
+int binsearch(size_t sz, int (*f)(size_t k, void *args), void *args)
+{
+	size_t lo = 0;
+	size_t hi = sz;
+
+	/* Invariants:
+	 *
+	 *  (hi == sz) || f(hi) == true
+	 *  (lo == 0 && f(0) == true) || fi(lo) == false
+	 */
+	while (hi - lo > 1) {
+		size_t mid = lo + (hi - lo) / 2;
+
+		if (f(mid, args))
+			hi = mid;
+		else
+			lo = mid;
+	}
+
+	if (lo)
+		return hi;
+
+	return f(0, args) ? 0 : 1;
+}
+
+void free_names(char **a)
+{
+	char **p;
+	if (!a) {
+		return;
+	}
+	for (p = a; *p; p++) {
+		reftable_free(*p);
+	}
+	reftable_free(a);
+}
+
+int names_length(char **names)
+{
+	char **p = names;
+	for (; *p; p++) {
+		/* empty */
+	}
+	return p - names;
+}
+
+void parse_names(char *buf, int size, char ***namesp)
+{
+	char **names = NULL;
+	size_t names_cap = 0;
+	size_t names_len = 0;
+
+	char *p = buf;
+	char *end = buf + size;
+	while (p < end) {
+		char *next = strchr(p, '\n');
+		if (next && next < end) {
+			*next = 0;
+		} else {
+			next = end;
+		}
+		if (p < next) {
+			if (names_len == names_cap) {
+				names_cap = 2 * names_cap + 1;
+				names = reftable_realloc(
+					names, names_cap * sizeof(*names));
+			}
+			names[names_len++] = xstrdup(p);
+		}
+		p = next + 1;
+	}
+
+	names = reftable_realloc(names, (names_len + 1) * sizeof(*names));
+	names[names_len] = NULL;
+	*namesp = names;
+}
+
+int names_equal(char **a, char **b)
+{
+	int i = 0;
+	for (; a[i] && b[i]; i++) {
+		if (strcmp(a[i], b[i])) {
+			return 0;
+		}
+	}
+
+	return a[i] == b[i];
+}
+
+int common_prefix_size(struct strbuf *a, struct strbuf *b)
+{
+	int p = 0;
+	for (; p < a->len && p < b->len; p++) {
+		if (a->buf[p] != b->buf[p])
+			break;
+	}
+
+	return p;
+}

reftable/basics.h

@@ -0,0 +1,60 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef BASICS_H
+#define BASICS_H
+
+/*
+ * miscellaneous utilities that are not provided by Git.
+ */
+
+#include "system.h"
+
+/* Bigendian en/decoding of integers */
+
+void put_be24(uint8_t *out, uint32_t i);
+uint32_t get_be24(uint8_t *in);
+void put_be16(uint8_t *out, uint16_t i);
+
+/*
+ * find smallest index i in [0, sz) at which f(i) is true, assuming
+ * that f is ascending. Return sz if f(i) is false for all indices.
+ *
+ * Contrary to bsearch(3), this returns something useful if the argument is not
+ * found.
+ */
+int binsearch(size_t sz, int (*f)(size_t k, void *args), void *args);
+
+/*
+ * Frees a NULL terminated array of malloced strings. The array itself is also
+ * freed.
+ */
+void free_names(char **a);
+
+/* parse a newline separated list of names. `size` is the length of the buffer,
+ * without terminating '\0'. Empty names are discarded. */
+void parse_names(char *buf, int size, char ***namesp);
+
+/* compares two NULL-terminated arrays of strings. */
+int names_equal(char **a, char **b);
+
+/* returns the array size of a NULL-terminated array of strings. */
+int names_length(char **names);
+
+/* Allocation routines; they invoke the functions set through
+ * reftable_set_alloc() */
+void *reftable_malloc(size_t sz);
+void *reftable_realloc(void *p, size_t sz);
+void reftable_free(void *p);
+void *reftable_calloc(size_t sz);
+
+/* Find the longest shared prefix size of `a` and `b` */
+struct strbuf;
+int common_prefix_size(struct strbuf *a, struct strbuf *b);
+
+#endif

reftable/basics_test.c

@@ -0,0 +1,98 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "system.h"
+
+#include "basics.h"
+#include "test_framework.h"
+#include "reftable-tests.h"
+
+struct binsearch_args {
+	int key;
+	int *arr;
+};
+
+static int binsearch_func(size_t i, void *void_args)
+{
+	struct binsearch_args *args = void_args;
+
+	return args->key < args->arr[i];
+}
+
+static void test_binsearch(void)
+{
+	int arr[] = { 2, 4, 6, 8, 10 };
+	size_t sz = ARRAY_SIZE(arr);
+	struct binsearch_args args = {
+		.arr = arr,
+	};
+
+	int i = 0;
+	for (i = 1; i < 11; i++) {
+		int res;
+		args.key = i;
+		res = binsearch(sz, &binsearch_func, &args);
+
+		if (res < sz) {
+			EXPECT(args.key < arr[res]);
+			if (res > 0) {
+				EXPECT(args.key >= arr[res - 1]);
+			}
+		} else {
+			EXPECT(args.key == 10 || args.key == 11);
+		}
+	}
+}
+
+static void test_names_length(void)
+{
+	char *a[] = { "a", "b", NULL };
+	EXPECT(names_length(a) == 2);
+}
+
+static void test_parse_names_normal(void)
+{
+	char in[] = "a\nb\n";
+	char **out = NULL;
+	parse_names(in, strlen(in), &out);
+	EXPECT(!strcmp(out[0], "a"));
+	EXPECT(!strcmp(out[1], "b"));
+	EXPECT(!out[2]);
+	free_names(out);
+}
+
+static void test_parse_names_drop_empty(void)
+{
+	char in[] = "a\n\n";
+	char **out = NULL;
+	parse_names(in, strlen(in), &out);
+	EXPECT(!strcmp(out[0], "a"));
+	EXPECT(!out[1]);
+	free_names(out);
+}
+
+static void test_common_prefix(void)
+{
+	struct strbuf s1 = STRBUF_INIT;
+	struct strbuf s2 = STRBUF_INIT;
+	strbuf_addstr(&s1, "abcdef");
+	strbuf_addstr(&s2, "abc");
+	EXPECT(common_prefix_size(&s1, &s2) == 3);
+	strbuf_release(&s1);
+	strbuf_release(&s2);
+}
+
+int basics_test_main(int argc, const char *argv[])
+{
+	RUN_TEST(test_common_prefix);
+	RUN_TEST(test_parse_names_normal);
+	RUN_TEST(test_parse_names_drop_empty);
+	RUN_TEST(test_binsearch);
+	RUN_TEST(test_names_length);
+	return 0;
+}

reftable/publicbasics.c

@@ -0,0 +1,65 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "reftable-malloc.h"
+
+#include "basics.h"
+#include "system.h"
+
+static void *(*reftable_malloc_ptr)(size_t sz);
+static void *(*reftable_realloc_ptr)(void *, size_t);
+static void (*reftable_free_ptr)(void *);
+
+void *reftable_malloc(size_t sz)
+{
+	if (reftable_malloc_ptr)
+		return (*reftable_malloc_ptr)(sz);
+	return malloc(sz);
+}
+
+void *reftable_realloc(void *p, size_t sz)
+{
+	if (reftable_realloc_ptr)
+		return (*reftable_realloc_ptr)(p, sz);
+	return realloc(p, sz);
+}
+
+void reftable_free(void *p)
+{
+	if (reftable_free_ptr)
+		reftable_free_ptr(p);
+	else
+		free(p);
+}
+
+void *reftable_calloc(size_t sz)
+{
+	void *p = reftable_malloc(sz);
+	memset(p, 0, sz);
+	return p;
+}
+
+void reftable_set_alloc(void *(*malloc)(size_t),
+			void *(*realloc)(void *, size_t), void (*free)(void *))
+{
+	reftable_malloc_ptr = malloc;
+	reftable_realloc_ptr = realloc;
+	reftable_free_ptr = free;
+}
+
+int hash_size(uint32_t id)
+{
+	switch (id) {
+	case 0:
+	case GIT_SHA1_FORMAT_ID:
+		return GIT_SHA1_RAWSZ;
+	case GIT_SHA256_FORMAT_ID:
+		return GIT_SHA256_RAWSZ;
+	}
+	abort();
+}

reftable/reftable-malloc.h

@@ -0,0 +1,18 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef REFTABLE_H
+#define REFTABLE_H
+
+#include <stddef.h>
+
+/* Overrides the functions to use for memory management. */
+void reftable_set_alloc(void *(*malloc)(size_t),
+			void *(*realloc)(void *, size_t), void (*free)(void *));
+
+#endif

reftable/reftable-tests.h

@@ -0,0 +1,22 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef REFTABLE_TESTS_H
+#define REFTABLE_TESTS_H
+
+int basics_test_main(int argc, const char **argv);
+int block_test_main(int argc, const char **argv);
+int merged_test_main(int argc, const char **argv);
+int record_test_main(int argc, const char **argv);
+int refname_test_main(int argc, const char **argv);
+int reftable_test_main(int argc, const char **argv);
+int stack_test_main(int argc, const char **argv);
+int tree_test_main(int argc, const char **argv);
+int reftable_dump_main(int argc, char *const *argv);
+
+#endif

reftable/system.h

@@ -0,0 +1,32 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef SYSTEM_H
+#define SYSTEM_H
+
+/* This header glues the reftable library to the rest of Git */
+
+#include "git-compat-util.h"
+#include "strbuf.h"
+#include "hash.h" /* hash ID, sizes.*/
+#include "dir.h" /* remove_dir_recursively, for tests.*/
+
+#include <zlib.h>
+
+#ifdef NO_UNCOMPRESS2
+/*
+ * This is uncompress2, which is only available in zlib >= 1.2.9
+ * (released as of early 2017)
+ */
+int uncompress2(Bytef *dest, uLongf *destLen, const Bytef *source,
+		uLong *sourceLen);
+#endif
+
+int hash_size(uint32_t id);
+
+#endif

reftable/test_framework.c

@@ -0,0 +1,23 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "system.h"
+#include "test_framework.h"
+
+#include "basics.h"
+
+void set_test_hash(uint8_t *p, int i)
+{
+	memset(p, (uint8_t)i, hash_size(GIT_SHA1_FORMAT_ID));
+}
+
+ssize_t strbuf_add_void(void *b, const void *data, size_t sz)
+{
+	strbuf_add(b, data, sz);
+	return sz;
+}

reftable/test_framework.h

@@ -0,0 +1,53 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef TEST_FRAMEWORK_H
+#define TEST_FRAMEWORK_H
+
+#include "system.h"
+#include "reftable-error.h"
+
+#define EXPECT_ERR(c)                                                  \
+	if (c != 0) {                                                  \
+		fflush(stderr);                                        \
+		fflush(stdout);                                        \
+		fprintf(stderr, "%s: %d: error == %d (%s), want 0\n",  \
+			__FILE__, __LINE__, c, reftable_error_str(c)); \
+		abort();                                               \
+	}
+
+#define EXPECT_STREQ(a, b)                                               \
+	if (strcmp(a, b)) {                                              \
+		fflush(stderr);                                          \
+		fflush(stdout);                                          \
+		fprintf(stderr, "%s:%d: %s (%s) != %s (%s)\n", __FILE__, \
+			__LINE__, #a, a, #b, b);                         \
+		abort();                                                 \
+	}
+
+#define EXPECT(c)                                                          \
+	if (!(c)) {                                                        \
+		fflush(stderr);                                            \
+		fflush(stdout);                                            \
+		fprintf(stderr, "%s: %d: failed assertion %s\n", __FILE__, \
+			__LINE__, #c);                                     \
+		abort();                                                   \
+	}
+
+#define RUN_TEST(f)                          \
+	fprintf(stderr, "running %s\n", #f); \
+	fflush(stderr);                      \
+	f();
+
+void set_test_hash(uint8_t *p, int i);
+
+/* Like strbuf_add, but suitable for passing to reftable_new_writer
+ */
+ssize_t strbuf_add_void(void *b, const void *data, size_t sz);
+
+#endif