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.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