Cleanup: libsqfs: move directory iteration out of the directory reader

Add a simple directory state object to the meta data reader and use
that to iterate directory entries. The code for reading the directory
listing is movde to readdir.c

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

5 files changed, 204 insertions, 108 deletions

diff --git a/include/sqfs/meta_reader.h b/include/sqfs/meta_reader.h
index e0dc186..149672b 100644
--- a/include/sqfs/meta_reader.h
+++ b/include/sqfs/meta_reader.h
@@ -21,6 +21,7 @@
 #define SQFS_META_READER_H
 
 #include "sqfs/predef.h"
+#include "sqfs/super.h"
 
 /**
  * @file meta_reader.h
@@ -47,6 +48,37 @@
  * from disk and reading transparently across block boarders if required.
  */
 
+/**
+ * @struct sqfs_readdir_state_t
+ *
+ * @brief Encapsulates state for simple directory reading
+ */
+struct sqfs_readdir_state_t {
+	struct {
+		sqfs_u64 block;
+		size_t offset;
+		size_t size;
+	} init, current;
+
+	size_t entries;
+
+	sqfs_u32 inum_base;
+	sqfs_u64 inode_block;
+};
+
+/**
+ * @brief Rewind a directory state object back to its starting location
+ *
+ * @memberof sqfs_readdir_state_t
+ *
+ * @param it A pointer to the directory state.
+ */
+static SQFS_INLINE void sqfs_readdir_state_reset(sqfs_readdir_state_t *s)
+{
+	s->current = s->init;
+	s->entries = 0;
+}
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -153,6 +185,57 @@ SQFS_API int sqfs_meta_reader_read_dir_ent(sqfs_meta_reader_t *m,
 					   sqfs_dir_entry_t **ent);
 
 /**
+ * @brief Initialize a state object for reading a directory
+ *
+ * @memberof sqfs_readdir_state_t
+ *
+ * This function initializes a simple state object to point to the
+ * location of a directory header and store the total, uncompressed
+ * size of the directory.
+ *
+ * The state object can be passed to @ref sqfs_meta_reader_readdir
+ * to read entries one-by-one.
+ *
+ * @param s A pointer to the state object to initialize.
+ * @param super A pointer to the super block, telling us where
+ *              the directory table starts.
+ * @param inode A pointer to a directory inode from which to get the
+ *              directory location.
+ *
+ * @return Zero on success, an @ref SQFS_ERROR value on
+ *         failure (e.g. the inode is not a directory inode).
+ */
+SQFS_API
+int sqfs_readdir_state_init(sqfs_readdir_state_t *s, const sqfs_super_t *super,
+			    const sqfs_inode_generic_t *inode);
+
+/**
+ * @brief Simple directory reading interface
+ *
+ * @memberof sqfs_meta_reader_t
+ *
+ * This function successively reads directory entries, transparently
+ * parsing and skipping across headers. The state is encapsulated in
+ * an external object that is passed in and the function seeks to the
+ * location, so one can swap between multiple states and read several
+ * directories interchangeably.
+ *
+ * @param m A pointer to a meta data reader.
+ * @param s A pointer to a directory state that is used and updated.
+ * @param ent Returns a pointer to a directory entry. Can be
+ *            released with a single @ref sqfs_free call.
+ * @param inum If not NULL, returns the decoded inode number.
+ * @param iref If not NULL, returns a reference to the inode.
+ *
+ * @return Zero on success, a negative @ref SQFS_ERROR number on failure,
+ *         a positive number if the end of the directory is reached.
+ */
+SQFS_API int sqfs_meta_reader_readdir(sqfs_meta_reader_t *m,
+				      sqfs_readdir_state_t *s,
+				      sqfs_dir_entry_t **ent,
+				      sqfs_u32 *inum, sqfs_u64 *iref);
+
+/**
  * @brief Read and decode an inode from a meta data reader.
  *
  * @memberof sqfs_meta_reader_t
diff --git a/include/sqfs/predef.h b/include/sqfs/predef.h
index a976cd4..3c13ef5 100644
--- a/include/sqfs/predef.h
+++ b/include/sqfs/predef.h
@@ -94,6 +94,7 @@ typedef struct sqfs_block_writer_t sqfs_block_writer_t;
 typedef struct sqfs_block_writer_stats_t sqfs_block_writer_stats_t;
 typedef struct sqfs_block_processor_stats_t sqfs_block_processor_stats_t;
 typedef struct sqfs_block_processor_desc_t sqfs_block_processor_desc_t;
+typedef struct sqfs_readdir_state_t sqfs_readdir_state_t;
 
 typedef struct sqfs_fragment_t sqfs_fragment_t;
 typedef struct sqfs_dir_header_t sqfs_dir_header_t;
diff --git a/lib/sqfs/dir_reader/dir_reader.c b/lib/sqfs/dir_reader/dir_reader.c
index 8a074aa..5ed0eff 100644
--- a/lib/sqfs/dir_reader/dir_reader.c
+++ b/lib/sqfs/dir_reader/dir_reader.c
@@ -105,29 +105,24 @@ int sqfs_dir_reader_open_dir(sqfs_dir_reader_t *rd,
 			     const sqfs_inode_generic_t *inode,
 			     sqfs_u32 flags)
 {
-	sqfs_u64 block_start;
-	size_t size, offset;
 	sqfs_u32 parent;
+	int ret;
 
 	if (flags & (~SQFS_DIR_OPEN_ALL_FLAGS))
 		return SQFS_ERROR_UNSUPPORTED;
 
-	if (inode->base.type == SQFS_INODE_DIR) {
-		parent = inode->data.dir.parent_inode;
-		size = inode->data.dir.size;
-		offset = inode->data.dir.offset;
-		block_start = inode->data.dir.start_block;
-	} else if (inode->base.type == SQFS_INODE_EXT_DIR) {
-		parent = inode->data.dir_ext.parent_inode;
-		size = inode->data.dir_ext.size;
-		offset = inode->data.dir_ext.offset;
-		block_start = inode->data.dir_ext.start_block;
-	} else {
-		return SQFS_ERROR_NOT_DIR;
-	}
+	ret = sqfs_readdir_state_init(&rd->it, rd->super, inode);
+	if (ret)
+		return ret;
 
 	if ((rd->flags & SQFS_DIR_READER_DOT_ENTRIES) &&
 	    !(flags & SQFS_DIR_OPEN_NO_DOT_ENTRIES)) {
+		if (inode->base.type == SQFS_INODE_EXT_DIR) {
+			parent = inode->data.dir_ext.parent_inode;
+		} else {
+			parent = inode->data.dir.parent_inode;
+		}
+
 		if (sqfs_dir_reader_dcache_find(rd, inode->base.inode_number,
 						&rd->cur_ref)) {
 			return SQFS_ERROR_NO_ENTRY;
@@ -146,21 +141,7 @@ int sqfs_dir_reader_open_dir(sqfs_dir_reader_t *rd,
 	}
 
 	rd->start_state = rd->state;
-
-	memset(&rd->hdr, 0, sizeof(rd->hdr));
-	rd->size = size;
-	rd->entries = 0;
-
-	block_start += rd->super->directory_table_start;
-
-	rd->dir_block_start = block_start;
-	rd->dir_offset = offset;
-	rd->start_size = size;
-
-	if (rd->size <= sizeof(rd->hdr))
-		return 0;
-
-	return sqfs_meta_reader_seek(rd->meta_dir, block_start, offset);
+	return 0;
 }
 
 static int mk_dummy_entry(const char *str, sqfs_dir_entry_t **out)
@@ -183,8 +164,6 @@ static int mk_dummy_entry(const char *str, sqfs_dir_entry_t **out)
 
 int sqfs_dir_reader_read(sqfs_dir_reader_t *rd, sqfs_dir_entry_t **out)
 {
-	sqfs_dir_entry_t *ent;
-	size_t count;
 	int err;
 
 	switch (rd->state) {
@@ -207,41 +186,8 @@ int sqfs_dir_reader_read(sqfs_dir_reader_t *rd, sqfs_dir_entry_t **out)
 		return SQFS_ERROR_SEQUENCE;
 	}
 
-	if (!rd->entries) {
-		if (rd->size <= sizeof(rd->hdr))
-			return 1;
-
-		err = sqfs_meta_reader_read_dir_header(rd->meta_dir, &rd->hdr);
-		if (err)
-			return err;
-
-		rd->size -= sizeof(rd->hdr);
-		rd->entries = rd->hdr.count + 1;
-	}
-
-	if (rd->size <= sizeof(*ent)) {
-		rd->size = 0;
-		rd->entries = 0;
-		return 1;
-	}
-
-	err = sqfs_meta_reader_read_dir_ent(rd->meta_dir, &ent);
-	if (err)
-		return err;
-
-	count = sizeof(*ent) + strlen((const char *)ent->name);
-
-	if (count > rd->size) {
-		rd->size = 0;
-		rd->entries = 0;
-	} else {
-		rd->size -= count;
-		rd->entries -= 1;
-	}
-
-	rd->inode_offset = ent->offset;
-	*out = ent;
-	return 0;
+	return sqfs_meta_reader_readdir(rd->meta_dir, &rd->it,
+					out, NULL, &rd->ent_ref);
 }
 
 int sqfs_dir_reader_rewind(sqfs_dir_reader_t *rd)
@@ -249,16 +195,9 @@ int sqfs_dir_reader_rewind(sqfs_dir_reader_t *rd)
 	if (rd->state == DIR_STATE_NONE)
 		return SQFS_ERROR_SEQUENCE;
 
-	memset(&rd->hdr, 0, sizeof(rd->hdr));
-	rd->size = rd->start_size;
-	rd->entries = 0;
+	sqfs_readdir_state_reset(&rd->it);
 	rd->state = rd->start_state;
-
-	if (rd->size <= sizeof(rd->hdr))
-		return 0;
-
-	return sqfs_meta_reader_seek(rd->meta_dir, rd->dir_block_start,
-				     rd->dir_offset);
+	return 0;
 }
 
 int sqfs_dir_reader_find(sqfs_dir_reader_t *rd, const char *name)
@@ -266,14 +205,9 @@ int sqfs_dir_reader_find(sqfs_dir_reader_t *rd, const char *name)
 	sqfs_dir_entry_t *ent;
 	int ret;
 
-	if (rd->state == DIR_STATE_NONE)
-		return SQFS_ERROR_SEQUENCE;
-
-	if (rd->size != rd->start_size || rd->state != rd->start_state) {
-		ret = sqfs_dir_reader_rewind(rd);
-		if (ret)
-			return ret;
-	}
+	ret = sqfs_dir_reader_rewind(rd);
+	if (ret != 0)
+		return ret;
 
 	do {
 		ret = sqfs_dir_reader_read(rd, &ent);
@@ -292,36 +226,25 @@ int sqfs_dir_reader_find(sqfs_dir_reader_t *rd, const char *name)
 int sqfs_dir_reader_get_inode(sqfs_dir_reader_t *rd,
 			      sqfs_inode_generic_t **inode)
 {
-	sqfs_u64 block_start;
-	sqfs_u16 offset;
+	sqfs_u64 ref;
 	int ret;
 
 	switch (rd->state) {
-	case DIR_STATE_DOT:
-		block_start = rd->cur_ref >> 16;
-		offset = rd->cur_ref & 0x0FFFF;
-		break;
-	case DIR_STATE_DOT_DOT:
-		block_start = rd->parent_ref >> 16;
-		offset = rd->parent_ref & 0x0FFFF;
-		break;
-	case DIR_STATE_ENTRIES:
-		block_start = rd->hdr.start_block;
-		offset = rd->inode_offset;
-		break;
+	case DIR_STATE_DOT:     ref = rd->cur_ref; break;
+	case DIR_STATE_DOT_DOT: ref = rd->parent_ref; break;
+	case DIR_STATE_ENTRIES: ref = rd->ent_ref; break;
 	default:
 		return SQFS_ERROR_SEQUENCE;
 	}
 
 	ret = sqfs_meta_reader_read_inode(rd->meta_inode, rd->super,
-					  block_start, offset, inode);
+					  ref >> 16, ref & 0x0FFFF, inode);
 	if (ret != 0)
 		return ret;
 
 	if ((*inode)->base.type == SQFS_INODE_DIR ||
 	    (*inode)->base.type == SQFS_INODE_EXT_DIR) {
 		sqfs_u32 inum = (*inode)->base.inode_number;
-		sqfs_u64 ref = (block_start << 16) | rd->inode_offset;
 
 		ret = sqfs_dir_reader_dcache_add(rd, inum, ref);
 		if (ret != 0)
diff --git a/lib/sqfs/dir_reader/internal.h b/lib/sqfs/dir_reader/internal.h
index cd20b69..4dbe728 100644
--- a/lib/sqfs/dir_reader/internal.h
+++ b/lib/sqfs/dir_reader/internal.h
@@ -38,14 +38,7 @@ struct sqfs_dir_reader_t {
 	sqfs_meta_reader_t *meta_inode;
 	const sqfs_super_t *super;
 
-	sqfs_dir_header_t hdr;
-	sqfs_u64 dir_block_start;
-	size_t entries;
-	size_t size;
-
-	size_t start_size;
-	sqfs_u16 dir_offset;
-	sqfs_u16 inode_offset;
+	sqfs_readdir_state_t it;
 
 	sqfs_u32 flags;
 
@@ -53,6 +46,7 @@ struct sqfs_dir_reader_t {
 	int state;
 	sqfs_u64 parent_ref;
 	sqfs_u64 cur_ref;
+	sqfs_u64 ent_ref;
 	rbtree_t dcache;
 };
 
diff --git a/lib/sqfs/readdir.c b/lib/sqfs/readdir.c
index 8899475..e2dbcd4 100644
--- a/lib/sqfs/readdir.c
+++ b/lib/sqfs/readdir.c
@@ -9,6 +9,8 @@
 
 #include "sqfs/meta_reader.h"
 #include "sqfs/error.h"
+#include "sqfs/super.h"
+#include "sqfs/inode.h"
 #include "sqfs/dir.h"
 #include "compat.h"
 
@@ -64,3 +66,96 @@ int sqfs_meta_reader_read_dir_ent(sqfs_meta_reader_t *m,
 	*result = out;
 	return 0;
 }
+
+int sqfs_readdir_state_init(sqfs_readdir_state_t *s, const sqfs_super_t *super,
+			    const sqfs_inode_generic_t *inode)
+{
+	memset(s, 0, sizeof(*s));
+
+	if (inode->base.type == SQFS_INODE_DIR) {
+		s->init.block = inode->data.dir.start_block;
+		s->init.offset = inode->data.dir.offset;
+		s->init.size = inode->data.dir.size;
+	} else if (inode->base.type == SQFS_INODE_EXT_DIR) {
+		s->init.block = inode->data.dir_ext.start_block;
+		s->init.offset = inode->data.dir_ext.offset;
+		s->init.size = inode->data.dir_ext.size;
+	} else {
+		return SQFS_ERROR_NOT_DIR;
+	}
+
+	s->init.block += super->directory_table_start;
+	s->current = s->init;
+	return 0;
+}
+
+int sqfs_meta_reader_readdir(sqfs_meta_reader_t *m, sqfs_readdir_state_t *it,
+			     sqfs_dir_entry_t **ent,
+			     sqfs_u32 *inum, sqfs_u64 *iref)
+{
+	size_t count;
+	int ret;
+
+	if (it->entries == 0) {
+		sqfs_dir_header_t hdr;
+
+		if (it->current.size <= sizeof(hdr))
+			goto out_eof;
+
+		ret = sqfs_meta_reader_seek(m, it->current.block,
+					    it->current.offset);
+		if (ret != 0)
+			return ret;
+
+		ret = sqfs_meta_reader_read_dir_header(m, &hdr);
+		if (ret != 0)
+			return ret;
+
+		sqfs_meta_reader_get_position(m, &it->current.block,
+					      &it->current.offset);
+
+		it->current.size -= sizeof(hdr);
+		it->entries = hdr.count + 1;
+		it->inum_base = hdr.inode_number;
+		it->inode_block = hdr.start_block;
+	}
+
+	if (it->current.size <= sizeof(**ent))
+		goto out_eof;
+
+	ret = sqfs_meta_reader_seek(m, it->current.block, it->current.offset);
+	if (ret != 0)
+		return ret;
+
+	ret = sqfs_meta_reader_read_dir_ent(m, ent);
+	if (ret)
+		return ret;
+
+	sqfs_meta_reader_get_position(m, &it->current.block,
+				      &it->current.offset);
+
+	it->current.size -= sizeof(**ent);
+	it->entries -= 1;
+
+	count = (*ent)->size + 1;
+
+	if (count >= it->current.size) {
+		it->current.size = 0;
+	} else {
+		it->current.size -= count;
+	}
+
+	if (inum != NULL)
+		*inum = it->inum_base + (*ent)->inode_diff;
+
+	if (iref != NULL) {
+		*iref = (sqfs_u64)it->inode_block << 16UL;
+		*iref |= (*ent)->offset;
+	}
+
+	return 0;
+out_eof:
+	it->current.size = 0;
+	it->entries = 0;
+	return 1;
+}