libio: consolidate add-hoc memory istream_t implementations

In several places, there are ad-hoc istream_t implementations that
read from a memory buffer to test something else stacked on top.

This commit consolidates those ad-hoc implmentations into a proper
one in libio, and uses the chance to remove external files for some
older tests that rely on file I/O instead.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 85 insertions, 0 deletions

diff --git a/lib/io/src/mem.c b/lib/io/src/mem.c
new file mode 100644
index 0000000..4e9f9af
--- /dev/null
+++ b/lib/io/src/mem.c
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * mem.c
+ *
+ * Copyright (C) 2023 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+#include "io/mem.h"
+#include "compat.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct {
+	istream_t base;
+
+	sqfs_u8 *buffer;
+	size_t bufsz;
+
+	const void *data;
+	size_t size;
+
+	char *name;
+} mem_istream_t;
+
+static int mem_in_precache(istream_t *strm)
+{
+	mem_istream_t *mem = (mem_istream_t *)strm;
+	size_t diff = mem->bufsz - strm->buffer_used;
+
+	if (diff > mem->size)
+		diff = mem->size;
+
+	if (diff > 0) {
+		memcpy(mem->buffer + strm->buffer_used, mem->data, diff);
+		strm->buffer_used += diff;
+		mem->data = (const char *)mem->data + diff;
+		mem->size -= diff;
+	}
+
+	if (mem->size == 0)
+		strm->eof = true;
+
+	return 0;
+}
+
+static const char *mem_in_get_filename(istream_t *strm)
+{
+	return ((mem_istream_t *)strm)->name;
+}
+
+static void mem_in_destroy(sqfs_object_t *obj)
+{
+	free(((mem_istream_t *)obj)->buffer);
+	free(((mem_istream_t *)obj)->name);
+	free(obj);
+}
+
+istream_t *istream_memory_create(const char *name, size_t bufsz,
+				 const void *data, size_t size)
+{
+	mem_istream_t *mem = calloc(1, sizeof(*mem));
+	istream_t *strm = (istream_t *)mem;
+
+	if (mem == NULL)
+		return NULL;
+
+	sqfs_object_init(mem, mem_in_destroy, NULL);
+
+	mem->name = strdup(name);
+	if (mem->name == NULL)
+		return sqfs_drop(mem);
+
+	mem->buffer = malloc(bufsz);
+	if (mem->buffer == NULL)
+		return sqfs_drop(mem);
+
+	mem->data = data;
+	mem->size = size;
+	mem->bufsz = bufsz;
+	strm->buffer = mem->buffer;
+	strm->precache = mem_in_precache;
+	strm->get_filename = mem_in_get_filename;
+	return strm;
+}