libpkgconf: add buffer management functions

Signed-off-by: Ariadne Conill <ariadne@ariadne.space>

Makefile.am

@@ -150,6 +150,7 @@ SUFFIXES=	.sh
 nobase_pkginclude_HEADERS = libpkgconf/bsdstubs.h libpkgconf/iter.h libpkgconf/libpkgconf.h libpkgconf/stdinc.h libpkgconf/libpkgconf-api.h
 libpkgconf_la_SOURCES  =	\
 		libpkgconf/audit.c		\
+		libpkgconf/buffer.c		\
 		libpkgconf/cache.c		\
 		libpkgconf/client.c		\
 		libpkgconf/pkg.c		\

libpkgconf/buffer.c

@@ -0,0 +1,51 @@
+/*
+ * buffer.c
+ * dynamically-managed buffers
+ *
+ * Copyright (c) 2024 pkgconf authors (see AUTHORS).
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include <libpkgconf/stdinc.h>
+#include <libpkgconf/libpkgconf.h>
+
+/*
+ * !doc
+ *
+ * libpkgconf `buffer` module
+ * ==========================
+ *
+ * The libpkgconf `buffer` module contains the functions related to managing
+ * dynamically-allocated buffers.
+ */
+
+void
+pkgconf_buffer_append(pkgconf_buffer_t *buffer, const char *text)
+{
+	size_t needed = strlen(text) + 1;
+
+	char *newbase = realloc(buffer->base, pkgconf_buffer_len(buffer) + needed);
+
+	/* XXX: silently failing here is antisocial */
+	if (newbase == NULL)
+		return;
+
+	char *newend = newbase + pkgconf_buffer_len(buffer);
+	pkgconf_strlcpy(newend, text, needed);
+
+	buffer->base = newbase;
+	buffer->end = newend;
+}
+
+void
+pkgconf_buffer_finalize(pkgconf_buffer_t *buffer)
+{
+	free(buffer->base);
+}

libpkgconf/libpkgconf.h

@@ -423,6 +423,22 @@ PKGCONF_API void pkgconf_path_free(pkgconf_list_t *dirlist);
 PKGCONF_API bool pkgconf_path_relocate(char *buf, size_t buflen);
 PKGCONF_API void pkgconf_path_copy_list(pkgconf_list_t *dst, const pkgconf_list_t *src);
 
+/* buffer.c */
+typedef struct pkgconf_buffer_ {
+	char *base;
+	char *end;
+} pkgconf_buffer_t;
+
+PKGCONF_API void pkgconf_buffer_append(pkgconf_buffer_t *buffer, const char *text);
+PKGCONF_API void pkgconf_buffer_finalize(pkgconf_buffer_t *buffer);
+static inline const char *pkgconf_buffer_str(const pkgconf_buffer_t *buffer) {
+	return buffer->base;
+}
+
+static inline size_t pkgconf_buffer_len(const pkgconf_buffer_t *buffer) {
+	return (size_t)(ptrdiff_t)(buffer->end - buffer->base);
+}
+
 #ifdef __cplusplus
 }
 #endif

meson.build

@@ -82,6 +82,7 @@ endif
 libpkgconf = library('pkgconf',
   'libpkgconf/argvsplit.c',
   'libpkgconf/audit.c',
+  'libpkgconf/buffer.c',
   'libpkgconf/bsdstubs.c',
   'libpkgconf/cache.c',
   'libpkgconf/client.c',