reader: expect iterator to return bool from _next

Currently the iterator's next function returns an int which
returns >0 on success, 0 on end of iterator and <0 on error.
This commit changes the generic iterator implementation to return
a bool instead of an int. The bool is true if the iterator has
more data and false if the iterator is at the end. The error
code is now passed as a pointer parameter to the next function.

include/sqsh_reader_private.h

@@ -47,7 +47,7 @@ extern "C" {
  */
 
 struct SqshReaderIteratorImpl {
-	int (*next)(void *iterator, size_t desired_size);
+	bool (*next)(void *iterator, size_t desired_size, int *err);
 	const uint8_t *(*data)(const void *iterator);
 	size_t (*size)(const void *iterator);
 };

lib/file/file_reader.c

@@ -39,9 +39,11 @@
 
 #include "../utils/utils.h"
 
-static int
-file_iterator_next(void *iterator, size_t desired_size) {
-	return sqsh_file_iterator_next(iterator, desired_size);
+static bool
+file_iterator_next(void *iterator, size_t desired_size, int *err) {
+	int rv = sqsh_file_iterator_next(iterator, desired_size);
+	*err = rv;
+	return rv > 0;
 }
 static const uint8_t *
 file_iterator_data(const void *iterator) {

lib/mapper/map_reader.c

@@ -36,10 +36,12 @@
 #include "../../include/sqsh_error.h"
 #include "../utils/utils.h"
 
-static int
-map_iterator_next(void *iterator, size_t desired_size) {
+static bool
+map_iterator_next(void *iterator, size_t desired_size, int *err) {
 	(void)desired_size;
-	return sqsh__map_iterator_next(iterator);
+	int rv = sqsh__map_iterator_next(iterator);
+	*err = rv;
+	return rv > 0;
 }
 static const uint8_t *
 map_iterator_data(const void *iterator) {

lib/metablock/metablock_reader.c

@@ -40,10 +40,12 @@
 #include "../../include/sqsh_error.h"
 #include "../utils/utils.h"
 
-static int
-metablock_iterator_next(void *iterator, size_t desired_size) {
+static bool
+metablock_iterator_next(void *iterator, size_t desired_size, int *err) {
 	(void)desired_size;
-	return sqsh__metablock_iterator_next(iterator);
+	int rv = sqsh__metablock_iterator_next(iterator);
+	*err = rv;
+	return rv > 0;
 }
 static const uint8_t *
 metablock_iterator_data(const void *iterator) {

lib/reader/reader.c

@@ -38,13 +38,15 @@
 
 #include <assert.h>
 
-static int
-reader_iterator_next(struct SqshReader *reader, size_t desired_size) {
-	int rv = reader->iterator_impl->next(reader->iterator, desired_size);
-	if (rv == 0) {
-		rv = -SQSH_ERROR_OUT_OF_BOUNDS;
+static bool
+reader_iterator_next(struct SqshReader *reader, size_t desired_size, int *err) {
+	bool has_next = reader->iterator_impl->next(reader->iterator, desired_size, err);
+	if (has_next == false && *err == 0) {
+		*err = -SQSH_ERROR_OUT_OF_BOUNDS;
+		return false;
+	} else {
+		return has_next;
 	}
-	return rv;
 }
 
 /**
@@ -72,7 +74,7 @@ reader_iterator_skip(
 
 	while (current_size <= *offset) {
 		*offset -= current_size;
-		rv = reader_iterator_next(reader, desired_size);
+		reader_iterator_next(reader, desired_size, &rv);
 		if (rv < 0) {
 			goto out;
 		}
@@ -133,7 +135,7 @@ reader_fill_buffer(struct SqshReader *reader, size_t size) {
 		}
 
 		iterator_offset = size - remaining_size;
-		rv = reader_iterator_next(reader, remaining_size);
+		reader_iterator_next(reader, remaining_size, &rv);
 		if (rv < 0) {
 			goto out;
 		}

test/reader/reader.c

@@ -59,17 +59,19 @@ test_iter_size(const void *data) {
 	}
 }
 
-static int
-test_iter_next(void *data, size_t desired_size) {
+static bool
+test_iter_next(void *data, size_t desired_size, int *err) {
 	struct TestIterator *iter = (struct TestIterator *)data;
 	(void)desired_size;
+	(void)err;
 	if (iter->remaining == 0) {
 		iter->current_data = "";
-		return 0;
+		return false;
 	}
 	iter->current_data = iter->data;
 	iter->remaining--;
-	return strlen(iter->current_data);
+
+	return true;
 }
 
 static const struct SqshReaderIteratorImpl test_iter = {