Add analog to gzread function

src/lz4stream.c

@@ -23,25 +23,6 @@
 #define LZ4S_B0_VERSION_MASK 0xC0
 #define LZ4S_B1_RESERVED_MASK 0x8f
 
-typedef struct lz4stream_t
-{
-  int     fd; // compressed file
-  void   *compressed_buffer; // buffer for compressed data
-  int     compressed_buffer_size;
-  void   *uncompressed_buffer;
-  int     decoded_bytes;
-  int     mode;
-  char   *error;
-
-  bool    block_checksum_flag;
-  bool    stream_checksum_flag;
-  int     block_size;
-  int     eof;
-  void   *offset;
-  void   *mapped_file;
-  size_t  file_size;
-} lz4stream;
-
 static void * read_stream_headers(lz4stream * lz)
 {
   uint8_t header[3] = {0, 0, 0};
@@ -257,6 +238,61 @@ int lz4stream_read_block(lz4stream * lz, void * tail)
    return lz->decoded_bytes;
 };
 
+int lz4stream_read(lz4stream *lz, void *buffer, unsigned int len) {
+
+  if(lz->eof && lz->tail == NULL) {
+    return 0;
+  }
+
+  void *tail = lz->tail;
+
+  int total_read = 0;
+  void *start = buffer;
+
+  if (tail != NULL) {
+
+    int bytes_left_in_buffer = lz->decoded_bytes - (tail - lz->uncompressed_buffer);
+
+    if (bytes_left_in_buffer >= len) {
+      memcpy(buffer, tail, len);
+      lz->tail += len;
+      return len;
+    } else if (bytes_left_in_buffer >= 0) {
+      memcpy(buffer, tail, bytes_left_in_buffer);
+      tail = NULL;
+      total_read += bytes_left_in_buffer;
+      start += bytes_left_in_buffer;
+    }
+
+  }
+
+  int bytes_read;
+
+  while ((bytes_read = lz4stream_read_block(lz, tail)) > 0) {
+
+    tail = NULL;
+    void *uncompressed_buffer = lz4stream_get_buffer(lz);
+
+    if (total_read + bytes_read >= len) {
+      int num_to_use = (bytes_read - (total_read + bytes_read - len));
+      memcpy(start, uncompressed_buffer, num_to_use);
+      total_read = len;
+      tail = uncompressed_buffer + num_to_use;
+      break;
+    } else {
+      memcpy(start, uncompressed_buffer, bytes_read);
+      total_read += bytes_read;
+      start += bytes_read;
+    }
+
+  }
+
+  lz->tail = tail;
+
+  return total_read;
+
+}
+
 int lz4stream_get_decoded_bytes(lz4stream * lz)
 {
   return lz->decoded_bytes;

src/lz4stream.h

@@ -1,7 +1,27 @@
 #ifndef LZ4_STREAM_H_INCLUDED_
 #define LZ4_STREAM_H_INCLUDED_
 
-typedef struct lz4stream_t lz4stream;
+#include <stdbool.h>
+
+typedef struct lz4stream_t
+{
+  int     fd; // compressed file
+  void   *compressed_buffer; // buffer for compressed data
+  int     compressed_buffer_size;
+  void   *uncompressed_buffer;
+  int     decoded_bytes;
+  int     mode;
+  char   *error;
+
+  bool    block_checksum_flag;
+  bool    stream_checksum_flag;
+  int     block_size;
+  int     eof;
+  void   *offset;
+  void   *mapped_file;
+  size_t  file_size;
+  void *tail;
+} lz4stream;
 
 lz4stream * lz4stream_open_read(const char * filename);
 
@@ -10,6 +30,7 @@ lz4stream * lz4stream_open_read(const char * filename);
 lz4stream * lz4stream_fdopen_read(int fd);
 int lz4stream_close(lz4stream * lz);
 int lz4stream_read_block(lz4stream * lz, void * tail);
+int lz4stream_read(lz4stream *file, void *buffer, unsigned int len);
 char * lz4stream_strerror(lz4stream * lz);
 
 /* access decoded data */