Refactoring the field encoder interface.

Replaced the confusing pb_enc_* functions with new pb_encode_* functions that
have a cleaner interface. Updated documentation.

Got rid of the endian_copy stuff in pb_encode.c, instead using C casts to do it automatically.
This makes the code safer and also reduces binary size by about 5%.

Fixes Issue 6.

1 files changed, 93 insertions, 77 deletions

diff --git a/pb_encode.c b/pb_encode.c
index 995eb3d..804c1a6 100644
--- a/pb_encode.c
+++ b/pb_encode.c
@@ -3,6 +3,7 @@
  * 2011 Petteri Aimonen <jpa@kapsi.fi>
  */
 
+#define NANOPB_INTERNALS
 #include "pb.h"
 #include "pb_encode.h"
 #include <string.h>
@@ -220,6 +221,40 @@ bool checkreturn pb_encode_varint(pb_ostream_t *stream, uint64_t value)
     return pb_write(stream, buffer, i);
 }
 
+bool checkreturn pb_encode_svarint(pb_ostream_t *stream, int64_t value)
+{
+    uint64_t zigzagged;
+    if (value < 0)
+        zigzagged = ~(value << 1);
+    else
+        zigzagged = value << 1;
+    
+    return pb_encode_varint(stream, zigzagged);
+}
+
+bool checkreturn pb_encode_fixed32(pb_ostream_t *stream, const void *value)
+{
+    #ifdef __BIG_ENDIAN__
+    uint8_t *bytes = value;
+    uint8_t lebytes[4] = {bytes[3], bytes[2], bytes[1], bytes[0]};
+    return pb_write(stream, lebytes, 4);
+    #else
+    return pb_write(stream, (uint8_t*)value, 4);
+    #endif
+}
+
+bool checkreturn pb_encode_fixed64(pb_ostream_t *stream, const void *value)
+{
+    #ifdef __BIG_ENDIAN__
+    uint8_t *bytes[8] = value;
+    uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4], 
+                          bytes[3], bytes[2], bytes[1], bytes[0]};
+    return pb_write(stream, lebytes, 8);
+    #else
+    return pb_write(stream, (uint8_t*)value, 8);
+    #endif
+}
+
 bool checkreturn pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
 {
     int tag = wiretype | (field_number << 3);
@@ -265,71 +300,85 @@ bool checkreturn pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, s
     return pb_write(stream, buffer, size);
 }
 
-/* Field encoders */
-
-/* Copy srcsize bytes from src so that values are casted properly.
- * On little endian machine, copy to start of dest
- * On big endian machine, copy to end of dest
- * destsize must always be larger than srcsize
- * 
- * Note: This is the reverse of the endian_copy in pb_decode.c.
- */
-static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
+bool checkreturn pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
 {
-#ifdef __BIG_ENDIAN__
-    memcpy((char*)dest + (destsize - srcsize), src, srcsize);
-#else
-    memcpy(dest, src, srcsize);
-#endif
+    /* First calculate the message size using a non-writing substream. */
+    pb_ostream_t substream = {0};
+    size_t size;
+    bool status;
+    
+    if (!pb_encode(&substream, fields, src_struct))
+        return false;
+    
+    size = substream.bytes_written;
+    
+    if (!pb_encode_varint(stream, size))
+        return false;
+    
+    if (stream->callback == NULL)
+        return pb_write(stream, NULL, size); /* Just sizing */
+    
+    if (stream->bytes_written + size > stream->max_size)
+        return false;
+        
+    /* Use a substream to verify that a callback doesn't write more than
+     * what it did the first time. */
+    substream.callback = stream->callback;
+    substream.state = stream->state;
+    substream.max_size = size;
+    substream.bytes_written = 0;
+    
+    status = pb_encode(&substream, fields, src_struct);
+    
+    stream->bytes_written += substream.bytes_written;
+    stream->state = substream.state;
+    
+    if (substream.bytes_written != size)
+        return false;
+    
+    return status;
 }
 
+/* Field encoders */
+
 bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
 {
     uint64_t value = 0;
-    endian_copy(&value, src, sizeof(value), field->data_size);
+    
+    switch (field->data_size)
+    {
+        case 1: value = *(uint8_t*)src; break;
+        case 2: value = *(uint16_t*)src; break;
+        case 4: value = *(uint32_t*)src; break;
+        case 8: value = *(uint64_t*)src; break;
+        default: return false;
+    }
+    
     return pb_encode_varint(stream, value);
 }
 
 bool checkreturn pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
 {
     uint64_t value = 0;
-    uint64_t zigzagged;
-    uint64_t signbitmask, xormask;
-    endian_copy(&value, src, sizeof(value), field->data_size);
     
-    signbitmask = (uint64_t)0x80 << (field->data_size * 8 - 8);
-    xormask = ((uint64_t)-1) >> (64 - field->data_size * 8);
-    if (value & signbitmask)
-        zigzagged = ((value ^ xormask) << 1) | 1;
-    else
-        zigzagged = value << 1;
+    switch (field->data_size)
+    {
+        case 4: value = *(int32_t*)src; break;
+        case 8: value = *(int64_t*)src; break;
+        default: return false;
+    }
     
-    return pb_encode_varint(stream, zigzagged);
+    return pb_encode_svarint(stream, value);
 }
 
 bool checkreturn pb_enc_fixed64(pb_ostream_t *stream, const pb_field_t *field, const void *src)
 {
-    #ifdef __BIG_ENDIAN__
-    uint8_t bytes[8] = {0};
-    memcpy(bytes, src, 8);
-    uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4], 
-                          bytes[3], bytes[2], bytes[1], bytes[0]};
-    return pb_write(stream, lebytes, 8);
-    #else
-    return pb_write(stream, (uint8_t*)src, 8);
-    #endif
+    return pb_encode_fixed64(stream, src);
 }
 
 bool checkreturn pb_enc_fixed32(pb_ostream_t *stream, const pb_field_t *field, const void *src)
 {
-    #ifdef __BIG_ENDIAN__
-    uint8_t bytes[4] = {0};
-    memcpy(bytes, src, 4);
-    uint8_t lebytes[4] = {bytes[3], bytes[2], bytes[1], bytes[0]};
-    return pb_write(stream, lebytes, 4);
-    #else
-    return pb_write(stream, (uint8_t*)src, 4);
-    #endif
+    return pb_encode_fixed32(stream, src);
 }
 
 bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
@@ -345,42 +394,9 @@ bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, co
 
 bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
 {
-    pb_ostream_t substream = {0};
-    size_t size;
-    bool status;
-    
     if (field->ptr == NULL)
         return false;
     
-    if (!pb_encode(&substream, (pb_field_t*)field->ptr, src))
-        return false;
-    
-    size = substream.bytes_written;
-    
-    if (!pb_encode_varint(stream, size))
-        return false;
-    
-    if (stream->callback == NULL)
-        return pb_write(stream, NULL, size); /* Just sizing */
-    
-    if (stream->bytes_written + size > stream->max_size)
-        return false;
-        
-    /* Use a substream to verify that a callback doesn't write more than
-     * what it did the first time. */
-    substream.callback = stream->callback;
-    substream.state = stream->state;
-    substream.max_size = size;
-    substream.bytes_written = 0;
-    
-    status = pb_encode(&substream, (pb_field_t*)field->ptr, src);
-    
-    stream->bytes_written += substream.bytes_written;
-    stream->state = substream.state;
-    
-    if (substream.bytes_written != size)
-        return false;
-    
-    return status;
+    return pb_encode_submessage(stream, (pb_field_t*)field->ptr, src);
 }