str: introduce `git_str` for internal, `git_buf` is externalethomson/gitstr

libgit2 has two distinct requirements that were previously solved by
`git_buf`.  We require:

1. A general purpose string class that provides a number of utility APIs
   for manipulating data (eg, concatenating, truncating, etc).
2. A structure that we can use to return strings to callers that they
   can take ownership of.

By using a single class (`git_buf`) for both of these purposes, we have
confused the API to the point that refactorings are difficult and
reasoning about correctness is also difficult.

Move the utility class `git_buf` to be called `git_str`: this represents
its general purpose, as an internal string buffer class.  The name also
is an homage to Junio Hamano ("gitstr").

The public API remains `git_buf`, and has a much smaller footprint.  It
is generally only used as an "out" param with strict requirements that
follow the documentation.  (Exceptions exist for some legacy APIs to
avoid breaking callers unnecessarily.)

Utility functions exist to convert a user-specified `git_buf` to a
`git_str` so that we can call internal functions, then converting it
back again.

1 files changed, 126 insertions, 0 deletions

diff --git a/src/buf.c b/src/buf.c
new file mode 100644
index 000000000..652f5dd52
--- /dev/null
+++ b/src/buf.c
@@ -0,0 +1,126 @@
+/*
+ * 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 "buf.h"
+#include "common.h"
+
+int git_buf_sanitize(git_buf *buf)
+{
+	GIT_ASSERT_ARG(buf);
+
+	if (buf->reserved > 0)
+		buf->ptr[0] = '\0';
+	else
+		buf->ptr = git_str__initstr;
+
+	buf->size = 0;
+	return 0;
+}
+
+int git_buf_tostr(git_str *out, git_buf *buf)
+{
+	GIT_ASSERT_ARG(out);
+	GIT_ASSERT_ARG(buf);
+
+	if (git_buf_sanitize(buf) < 0)
+		return -1;
+
+	out->ptr = buf->ptr;
+	out->asize = buf->reserved;
+	out->size = buf->size;
+
+	buf->ptr = git_str__initstr;
+	buf->reserved = 0;
+	buf->size = 0;
+
+	return 0;
+}
+
+int git_buf_fromstr(git_buf *out, git_str *str)
+{
+	GIT_ASSERT_ARG(out);
+	GIT_ASSERT_ARG(str);
+
+	out->ptr = str->ptr;
+	out->reserved = str->asize;
+	out->size = str->size;
+
+	str->ptr = git_str__initstr;
+	str->asize = 0;
+	str->size = 0;
+
+	return 0;
+}
+
+void git_buf_dispose(git_buf *buf)
+{
+	if (!buf)
+		return;
+
+	if (buf->ptr != git_str__initstr)
+		git__free(buf->ptr);
+
+	buf->ptr = git_str__initstr;
+	buf->reserved = 0;
+	buf->size = 0;
+}
+
+#ifndef GIT_DEPRECATE_HARD
+int git_buf_grow(git_buf *buffer, size_t target_size)
+{
+	char *newptr;
+
+	if (buffer->reserved >= target_size)
+		return 0;
+
+	if (buffer->ptr == git_str__initstr)
+		newptr = git__malloc(target_size);
+	else
+		newptr = git__realloc(buffer->ptr, target_size);
+
+	if (!newptr)
+		return -1;
+
+	buffer->ptr = newptr;
+	buffer->reserved = target_size;
+	return 0;
+}
+
+int git_buf_set(git_buf *buffer, const void *data, size_t datalen)
+{
+	size_t alloclen;
+
+	GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, datalen, 1);
+
+	if (git_buf_grow(buffer, alloclen) < 0)
+		return -1;
+
+	memmove(buffer->ptr, data, datalen);
+	buffer->size = datalen;
+	buffer->ptr[buffer->size] = '\0';
+
+	return 0;
+}
+
+int git_buf_is_binary(const git_buf *buf)
+{
+	git_str str = GIT_STR_INIT_CONST(buf->ptr, buf->size);
+	return git_str_is_binary(&str);
+}
+
+int git_buf_contains_nul(const git_buf *buf)
+{
+	git_str str = GIT_STR_INIT_CONST(buf->ptr, buf->size);
+	return git_str_contains_nul(&str);
+}
+
+void git_buf_free(git_buf *buffer)
+{
+	git_buf_dispose(buffer);
+}
+
+#endif