3 files changed, 127 insertions, 1 deletions

diff --git a/include/sqfs/io.h b/include/sqfs/io.h
index 0f980d6..a544875 100644
--- a/include/sqfs/io.h
+++ b/include/sqfs/io.h
@@ -142,6 +142,17 @@ extern "C" {
  */
 SQFS_API sqfs_file_t *sqfs_open_file(const char *filename, int flags);
 
+/**
+ * @brief Get a read-only file implementation that represents standard input
+ *
+ * This function creates a read-only file that represents STDIN. The file
+ * supports reading up to a specified number of bytes and only allows
+ * reading sequentially.
+ *
+ * @param size The alleged "size" of the file.
+ */
+SQFS_API sqfs_file_t *sqfs_get_stdin_file(uint64_t size);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/sqfs/Makemodule.am b/lib/sqfs/Makemodule.am
index 7199441..b58a28b 100644
--- a/lib/sqfs/Makemodule.am
+++ b/lib/sqfs/Makemodule.am
@@ -13,7 +13,7 @@ libsquashfs_la_SOURCES += lib/sqfs/read_super.c lib/sqfs/meta_reader.c
 libsquashfs_la_SOURCES += lib/sqfs/read_inode.c lib/sqfs/write_inode.c
 libsquashfs_la_SOURCES += lib/sqfs/dir_writer.c lib/sqfs/xattr_reader.c
 libsquashfs_la_SOURCES += lib/sqfs/read_table.c lib/sqfs/comp/compressor.c
-libsquashfs_la_SOURCES += lib/sqfs/comp/internal.h
+libsquashfs_la_SOURCES += lib/sqfs/io_stdin.c lib/sqfs/comp/internal.h
 libsquashfs_la_SOURCES += lib/sqfs/blk_proc/process_block.c
 libsquashfs_la_SOURCES += lib/sqfs/blk_proc/internal.h
 libsquashfs_la_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/lib/sqfs/io_stdin.c b/lib/sqfs/io_stdin.c
new file mode 100644
index 0000000..a65fa0f
--- /dev/null
+++ b/lib/sqfs/io_stdin.c
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * io_stdin.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#define SQFS_BUILDING_DLL
+#include "config.h"
+
+#include "sqfs/io.h"
+#include "sqfs/error.h"
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+
+
+typedef struct {
+	sqfs_file_t base;
+
+	uint64_t offset;
+	uint64_t size;
+} sqfs_file_stdin_t;
+
+
+static void stdin_destroy(sqfs_file_t *base)
+{
+	free(base);
+}
+
+static int stdin_read_at(sqfs_file_t *base, uint64_t offset,
+			 void *buffer, size_t size)
+{
+	sqfs_file_stdin_t *file = (sqfs_file_stdin_t *)base;
+	size_t temp_size = 0;
+	uint8_t *temp = NULL;
+	uint64_t diff;
+	ssize_t ret;
+
+	if (offset < file->offset)
+		return SQFS_ERROR_IO;
+
+	if (offset > file->offset) {
+		temp_size = 1024;
+		temp = alloca(temp_size);
+	}
+
+	if (offset >= file->size || (offset + size) > file->size)
+		return SQFS_ERROR_OUT_OF_BOUNDS;
+
+	while (size > 0) {
+		if (offset > file->offset) {
+			diff = file->offset - offset;
+			diff = diff > (uint64_t)temp_size ? temp_size : diff;
+
+			ret = read(STDIN_FILENO, temp, diff);
+		} else {
+			ret = read(STDIN_FILENO, buffer, size);
+		}
+
+		if (ret < 0) {
+			if (errno == EINTR)
+				continue;
+			return SQFS_ERROR_IO;
+		}
+
+		if (ret == 0)
+			return SQFS_ERROR_OUT_OF_BOUNDS;
+
+		if (offset <= file->offset) {
+			buffer = (char *)buffer + ret;
+			size -= ret;
+			offset += ret;
+		}
+
+		file->offset += ret;
+	}
+
+	return 0;
+}
+
+static int stdin_write_at(sqfs_file_t *base, uint64_t offset,
+			  const void *buffer, size_t size)
+{
+	(void)base; (void)offset; (void)buffer; (void)size;
+	return SQFS_ERROR_IO;
+}
+
+static uint64_t stdin_get_size(const sqfs_file_t *base)
+{
+	return ((const sqfs_file_stdin_t *)base)->size;
+}
+
+static int stdin_truncate(sqfs_file_t *base, uint64_t size)
+{
+	(void)base; (void)size;
+	return SQFS_ERROR_IO;
+}
+
+sqfs_file_t *sqfs_get_stdin_file(uint64_t size)
+{
+	sqfs_file_stdin_t *file = calloc(1, sizeof(*file));
+	sqfs_file_t *base = (sqfs_file_t *)file;
+
+	if (file == NULL)
+		return NULL;
+
+	file->size = size;
+	base->destroy = stdin_destroy;
+	base->read_at = stdin_read_at;
+	base->write_at = stdin_write_at;
+	base->get_size = stdin_get_size;
+	base->truncate = stdin_truncate;
+	return base;
+}