1 files changed, 52 insertions, 6 deletions

diff --git a/librsync/librsync.go b/librsync/librsync.go
index 641e480..1ffc7ec 100644
--- a/librsync/librsync.go
+++ b/librsync/librsync.go
@@ -6,6 +6,7 @@ package librsync
 #include <stdio.h>
 #include <librsync.h>
 #include <stdlib.h>
+#include <stdbool.h>
 
 static inline rs_buffers_t* new_rs_buffers() {
 	return (rs_buffers_t*) malloc(sizeof(rs_buffers_t));
@@ -17,6 +18,27 @@ rs_result patchCallback(void* _patcher, rs_long_t pos, size_t* len, void** _buf)
 	return patchCallbackGo(_patcher, pos, len, _buf);
 }
 
+#ifndef RS_DEFAULT_STRONG_LEN
+// librsync >= 1.0.0, 0 is the full size (32 bytes)
+#define DEFAULT_STRONG_LEN 0
+#else
+// librsync < 1.0.0, using md4 (8 bytes)
+#define DEFAULT_STRONG_LEN RS_DEFAULT_STRONG_LEN
+#endif
+
+static inline rs_job_t* sig_begin(size_t new_block_len, size_t strong_sum_len, bool compat) {
+#ifndef RS_DEFAULT_STRONG_LEN
+	// librsync >= 1.0.0, supporting the newer hash function (blake2b)
+	if (compat) {
+		return rs_sig_begin(new_block_len, strong_sum_len, RS_MD4_SIG_MAGIC);
+	}
+	return rs_sig_begin(new_block_len, strong_sum_len, RS_BLAKE2_SIG_MAGIC);
+#else
+	// not supporting the newer hash function, fall back to the md4 hash
+	return rs_sig_begin(new_block_len, strong_sum_len);
+#endif
+}
+
 */
 import "C"
 
@@ -32,6 +54,11 @@ const (
 	outbufSize = 16 * 1024
 )
 
+const (
+	DefaultBlockLen  = C.RS_DEFAULT_BLOCK_LEN
+	DefaultStrongLen = C.DEFAULT_STRONG_LEN
+)
+
 var (
 	ErrInputEnded = errors.New("Input ended (possibly unexpected)")
 	ErrBadMagic   = errors.New("Bad magic number. Probably not an librsync file.")
@@ -74,24 +101,43 @@ func newJob(input io.Reader) (job *Job, err error) {
 	return
 }
 
-// NewDefaultSignatureGen is like NewSignatureGen, but uses default values for blocklen and stronglen.
+// Config sets parameters for NewSignatureGen. May be the zero value for default
+// values.
+type Config struct {
+	BlockLen  uint // length of a block, e.g. 2048
+	StrongLen uint // length of a strong hash, e.g. 32 or 0
+	CompatMD4 bool // enable for compatibility with librsync < 1.0.0
+}
+
+func (c *Config) setup() {
+	if c.BlockLen == 0 {
+		c.BlockLen = DefaultBlockLen
+	}
+	if c.StrongLen == 0 {
+		c.StrongLen = DefaultStrongLen
+	}
+}
+
+// NewDefaultSignatureGen is like NewSignatureGen, but uses the default
+// configuration.
 func NewDefaultSignatureGen(basis io.Reader) (job *Job, err error) {
-	job, err = NewSignatureGen(C.RS_DEFAULT_BLOCK_LEN, C.RS_DEFAULT_STRONG_LEN, basis)
+	job, err = NewSignatureGen(Config{}, basis)
 	return
 }
 
 // NewSignatureGen creates a signature generation job.
 //
-// blocklen is the length of a block.
-// stronglen is the length of the stong hash.
+// config is a Config object for more options.
 // basis is an io.Reader that provides data of the basis file.
-func NewSignatureGen(blocklen, stronglen uint, basis io.Reader) (job *Job, err error) {
+func NewSignatureGen(config Config, basis io.Reader) (job *Job, err error) {
 	job, err = newJob(basis)
 	if err != nil {
 		return
 	}
 
-	job.job = C.rs_sig_begin(C.size_t(blocklen), C.size_t(stronglen))
+	config.setup()
+
+	job.job = C.sig_begin(C.size_t(config.BlockLen), C.size_t(config.StrongLen), C.bool(config.CompatMD4))
 	if job.job == nil {
 		job.Close()
 		return nil, errors.New("rs_sig_begin failed")