reader: move skip to the implementors.

This allows implementors of the generic reader to implement optimized
skip functions.

include/sqsh_reader_private.h

@@ -48,6 +48,7 @@ extern "C" {
 
 struct SqshReaderIteratorImpl {
 	bool (*next)(void *iterator, size_t desired_size, int *err);
+	int (*skip)(void *iterator, sqsh_index_t *offset, size_t desired_size);
 	const uint8_t *(*data)(const void *iterator);
 	size_t (*size)(const void *iterator);
 };

lib/file/file_reader.c

@@ -43,6 +43,27 @@ static bool
 file_iterator_next(void *iterator, size_t desired_size, int *err) {
 	return sqsh_file_iterator_next(iterator, desired_size, err);
 }
+static int
+file_iterator_skip(void *iterator, sqsh_index_t *offset, size_t desired_size) {
+	int rv = 0;
+
+	size_t current_size = sqsh_file_iterator_size(iterator);
+	while (current_size <= *offset) {
+		*offset -= current_size;
+		bool has_next = sqsh_file_iterator_next(iterator, desired_size, &rv);
+		if (rv < 0) {
+			goto out;
+		} else if (!has_next) {
+			rv = -SQSH_ERROR_OUT_OF_BOUNDS;
+			goto out;
+		}
+		current_size = sqsh_file_iterator_size(iterator);
+	}
+
+	rv = 0;
+out:
+	return rv;
+}
 static const uint8_t *
 file_iterator_data(const void *iterator) {
 	return sqsh_file_iterator_data(iterator);
@@ -54,6 +75,7 @@ file_iterator_size(const void *iterator) {
 
 static const struct SqshReaderIteratorImpl file_reader_impl = {
 		.next = file_iterator_next,
+		.skip = file_iterator_skip,
 		.data = file_iterator_data,
 		.size = file_iterator_size,
 };

lib/mapper/map_reader.c

@@ -41,6 +41,28 @@ map_iterator_next(void *iterator, size_t desired_size, int *err) {
 	(void)desired_size;
 	return sqsh__map_iterator_next(iterator, err);
 }
+static int
+map_iterator_skip(void *iterator, sqsh_index_t *offset, size_t desired_size) {
+	(void)desired_size;
+	int rv = 0;
+
+	size_t current_size = sqsh__map_iterator_size(iterator);
+	while (current_size <= *offset) {
+		*offset -= current_size;
+		bool has_next = sqsh__map_iterator_next(iterator, &rv);
+		if (rv < 0) {
+			goto out;
+		} else if (!has_next) {
+			rv = -SQSH_ERROR_OUT_OF_BOUNDS;
+			goto out;
+		}
+		current_size = sqsh__map_iterator_size(iterator);
+	}
+
+	rv = 0;
+out:
+	return rv;
+}
 static const uint8_t *
 map_iterator_data(const void *iterator) {
 	return sqsh__map_iterator_data(iterator);
@@ -52,6 +74,7 @@ map_iterator_size(const void *iterator) {
 
 static const struct SqshReaderIteratorImpl map_reader_impl = {
 		.next = map_iterator_next,
+		.skip = map_iterator_skip,
 		.data = map_iterator_data,
 		.size = map_iterator_size,
 };

lib/metablock/metablock_reader.c

@@ -45,6 +45,28 @@ metablock_iterator_next(void *iterator, size_t desired_size, int *err) {
 	(void)desired_size;
 	return sqsh__metablock_iterator_next(iterator, err);
 }
+static int
+metablock_iterator_skip(void *iterator, sqsh_index_t *offset, size_t desired_size) {
+	(void)desired_size;
+	int rv = 0;
+
+	size_t current_size = sqsh__metablock_iterator_size(iterator);
+	while (current_size <= *offset) {
+		*offset -= current_size;
+		bool has_next = sqsh__metablock_iterator_next(iterator, &rv);
+		if (rv < 0) {
+			goto out;
+		} else if (!has_next) {
+			rv = -SQSH_ERROR_OUT_OF_BOUNDS;
+			goto out;
+		}
+		current_size = sqsh__metablock_iterator_size(iterator);
+	}
+
+	rv = 0;
+out:
+	return rv;
+}
 static const uint8_t *
 metablock_iterator_data(const void *iterator) {
 	return sqsh__metablock_iterator_data(iterator);
@@ -56,6 +78,7 @@ metablock_iterator_size(const void *iterator) {
 
 static const struct SqshReaderIteratorImpl metablock_reader_impl = {
 		.next = metablock_iterator_next,
+		.skip = metablock_iterator_skip,
 		.data = metablock_iterator_data,
 		.size = metablock_iterator_size,
 };

lib/reader/reader.c

@@ -50,43 +50,6 @@ reader_iterator_next(struct SqshReader *reader, size_t desired_size, int *err) {
 	}
 }
 
-/**
- * @brief      Skips the iterator until the offset is reached.
- *
- * This is a naiv implementation that just calls next until the offset is
- * reached.
- *
- * TODO: Implement a iterator specific skip function.
- *
- * @param      reader        The reader
- * @param      offset        The offset
- * @param[in]  desired_size  The desired size
- *
- * @return     0 on success, negative on error.
- */
-static int
-reader_iterator_skip(
-		struct SqshReader *reader, sqsh_index_t *offset, size_t desired_size) {
-	int rv = 0;
-	void *iterator = reader->iterator;
-	const struct SqshReaderIteratorImpl *impl = reader->iterator_impl;
-
-	size_t current_size = impl->size(iterator);
-
-	while (current_size <= *offset) {
-		*offset -= current_size;
-		reader_iterator_next(reader, desired_size, &rv);
-		if (rv < 0) {
-			goto out;
-		}
-		current_size = impl->size(iterator);
-	}
-
-	rv = 0;
-out:
-	return rv;
-}
-
 int
 sqsh__reader_init(
 		struct SqshReader *reader,
@@ -197,7 +160,7 @@ handle_mapped(struct SqshReader *reader, sqsh_index_t offset, size_t size) {
 		goto out;
 	}
 
-	rv = reader_iterator_skip(reader, &offset, size);
+	rv = impl->skip(iterator, &offset, size);
 	if (rv < 0) {
 		goto out;
 	}

test/reader/reader.c

@@ -74,8 +74,31 @@ test_iter_next(void *data, size_t desired_size, int *err) {
 	return true;
 }
 
+static int
+test_iter_skip(void *iterator, sqsh_index_t *offset, size_t desired_size) {
+	int rv = 0;
+
+	size_t current_size = test_iter_size(iterator);
+	while (current_size <= *offset) {
+		*offset -= current_size;
+		bool has_next = test_iter_next(iterator, desired_size, &rv);
+		if (rv < 0) {
+			goto out;
+		} else if (!has_next) {
+			rv = -SQSH_ERROR_OUT_OF_BOUNDS;
+			goto out;
+		}
+		current_size = test_iter_size(iterator);
+	}
+
+	rv = 0;
+out:
+	return rv;
+}
+
 static const struct SqshReaderIteratorImpl test_iter = {
 		.next = test_iter_next,
+		.skip = test_iter_skip,
 		.data = test_iter_data,
 		.size = test_iter_size,
 };