1 files changed, 65 insertions, 2 deletions

diff --git a/lib/sqfshelper/io_stdin.c b/lib/sqfshelper/io_stdin.c
index 6cb45d4..8568f5e 100644
--- a/lib/sqfshelper/io_stdin.c
+++ b/lib/sqfshelper/io_stdin.c
@@ -11,12 +11,14 @@
 
 #include <stdlib.h>
 #include <unistd.h>
+#include <string.h>
 #include <errno.h>
 
 
 typedef struct {
 	sqfs_file_t base;
 
+	const sparse_map_t *map;
 	uint64_t offset;
 	uint64_t size;
 } sqfs_file_stdin_t;
@@ -78,6 +80,60 @@ static int stdin_read_at(sqfs_file_t *base, uint64_t offset,
 	return 0;
 }
 
+static int stdin_read_condensed(sqfs_file_t *base, uint64_t offset,
+				void *buffer, size_t size)
+{
+	sqfs_file_stdin_t *file = (sqfs_file_stdin_t *)base;
+	uint64_t poffset = 0, src_start;
+	size_t dst_start, diff, count;
+	const sparse_map_t *it;
+	int err;
+
+	memset(buffer, 0, size);
+
+	for (it = file->map; it != NULL; it = it->next) {
+		if (it->offset + it->count <= offset) {
+			poffset += it->count;
+			continue;
+		}
+
+		if (it->offset >= offset + size) {
+			poffset += it->count;
+			continue;
+		}
+
+		count = size;
+
+		if (offset + count >= it->offset + it->count)
+			count = it->offset + it->count - offset;
+
+		if (it->offset < offset) {
+			diff = offset - it->offset;
+
+			src_start = poffset + diff;
+			dst_start = 0;
+			count -= diff;
+		} else if (it->offset > offset) {
+			diff = it->offset - offset;
+
+			src_start = poffset;
+			dst_start = diff;
+		} else {
+			src_start = poffset;
+			dst_start = 0;
+		}
+
+		err = stdin_read_at(base, src_start,
+				    (char *)buffer + dst_start, count);
+		if (err)
+			return err;
+
+		poffset += it->count;
+	}
+
+	return 0;
+}
+
 static int stdin_write_at(sqfs_file_t *base, uint64_t offset,
 			  const void *buffer, size_t size)
 {
@@ -96,7 +152,7 @@ static int stdin_truncate(sqfs_file_t *base, uint64_t size)
 	return SQFS_ERROR_IO;
 }
 
-sqfs_file_t *sqfs_get_stdin_file(uint64_t size)
+sqfs_file_t *sqfs_get_stdin_file(const sparse_map_t *map, uint64_t size)
 {
 	sqfs_file_stdin_t *file = calloc(1, sizeof(*file));
 	sqfs_file_t *base = (sqfs_file_t *)file;
@@ -105,10 +161,17 @@ sqfs_file_t *sqfs_get_stdin_file(uint64_t size)
 		return NULL;
 
 	file->size = size;
+	file->map = map;
+
 	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;
+
+	if (map == NULL) {
+		base->read_at = stdin_read_at;
+	} else {
+		base->read_at = stdin_read_condensed;
+	}
 	return base;
 }