First version of decoding

git-svn-id: https://svn.kapsi.fi/jpa/nanopb@942 e3a754e5-d11d-0410-8d38-ebb782a927b9

pb_decode.c

@@ -0,0 +1,274 @@
+/* pb_decode.c -- decode a protobuf using callback functions
+ *
+ * 2011 Petteri Aimonen <jpa@kapsi.fi>
+ */
+
+#include "pb_decode.h"
+
+const pb_decoder_t PB_DECODERS[PB_LAST_ACT] = {
+    NULL,
+    &pb_dec_uint32,
+    &pb_dec_sint32,
+    &pb_dec_uint32, // Cast to int32
+    &pb_dec_fixed32,
+    &pb_dec_fixed32, // Cast to int32
+    &pb_dec_uint64,
+    &pb_dec_sint64,
+    &pb_dec_uint64, // Cast to int64
+    &pb_dec_fixed64,
+    &pb_dec_fixed64, // Cast to int64
+    &pb_dec_bool,
+    &pb_dec_float,
+    &pb_dec_double,
+    &pb_dec_bytes,
+    &pb_dec_string,
+    &pb_dec_submessage
+};
+
+enum wire_type {
+    WT_VARINT = 0,
+    WT_64BIT  = 1,
+    WT_STRING = 2,
+    WT_32BIT  = 5
+};
+
+// Note: pb_decode_varint32 is a bit un-orthodox:
+// it will refuse to decode values that exceed uint32 range.
+// The Google implementation would simply cast to 32 bits.
+bool pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
+{
+    char byte;
+    int bitpos = 0;
+    *dest = 0;
+    
+    while (bitpos < 32 && pb_read(stream, &byte, 1))
+    {
+        *dest |= (byte & 0x7F) << bitpos;
+        bitpos += 7;
+        
+        if (!(byte & 0x80))
+            return true;
+    }
+    
+    return false;
+}
+
+bool pb_decode_varint64(pb_istream_t *stream, uint64_t *dest)
+{
+    char byte;
+    int bitpos = 0;
+    *dest = 0;
+    
+    while (bitpos < 64 && pb_read(stream, &byte, 1))
+    {
+        *dest |= (byte & 0x7F) << bitpos;
+        bitpos += 7;
+        
+        if (!(byte & 0x80))
+            return true;
+    }
+    
+    return false;
+}
+
+bool pb_skip_varint(pb_istream_t *stream)
+{
+    char byte;
+    do
+    {
+        if (!pb_read(stream, &byte, 1))
+            return false;
+    } while (byte & 0x80);
+    return true;
+}
+
+bool pb_skip_string(pb_istream_t *stream)
+{
+    uint32_t length;
+    if (!pb_decode_varint32(stream, &length))
+        return false;
+    
+    return pb_read(stream, NULL, length);
+}
+
+bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest)
+{
+    while (stream->bytes_left)
+    {
+        uint32_t temp;
+        if (!pb_decode_varint32(stream, &temp))
+            return false;
+        
+        int field_number = temp >> 3;
+        int wire_type = temp & 7;
+        
+        const pb_field_t *field = fields;
+        while (field->field_number != 0)
+        {
+            if (field->field_number != field_number)
+            {
+                field++;
+                continue;
+            }
+            
+            void *destfield = dest + field->offset; 
+            
+            if (field->action == PB_ACT_HAS)
+            {
+                *(bool*)destfield = true;
+                field++;
+                continue;
+            }
+            
+            pb_decoder_t func = PB_DECODERS[field->action];
+            if (!func(stream, field, destfield))
+                return false;
+            
+            break;
+        }
+        
+        if (field->field_number == 0) // No match found, skip data
+        {
+            bool status = false;
+            switch (wire_type)
+            {
+                case WT_VARINT:
+                    status = pb_skip_varint(stream);
+                    break;
+                
+                case WT_64BIT:
+                    status = pb_read(stream, NULL, 8);
+                    break;
+                
+                case WT_STRING:
+                    status = pb_skip_string(stream);
+                    break;
+                
+                case WT_32BIT:
+                    status = pb_read(stream, NULL, 4);
+                    break;
+            }
+            
+            if (!status)
+                return false;
+        }
+    }
+    
+    return true;
+}
+
+bool pb_dec_uint32(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    return pb_decode_varint32(stream, (uint32_t*)dest);
+}
+
+bool pb_dec_sint32(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint32_t *x = (uint32_t*)dest;
+    bool status = pb_decode_varint32(stream, x);
+    *x = (*x >> 1) ^ -(int32_t)(*x & 1);
+    return status;
+}
+
+bool pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    char bytes[4] = {0};
+    bool status = pb_read(stream, bytes, 4);
+    *(uint32_t*)dest = 
+        bytes[0] | ((uint32_t)bytes[1] << 8) |
+        ((uint32_t)bytes[2] << 16) | ((uint32_t)bytes[3] << 24);
+    return status;
+}
+
+bool pb_dec_uint64(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    return pb_decode_varint64(stream, (uint64_t*)dest);
+}
+
+bool pb_dec_sint64(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint64_t *x = (uint64_t*)dest;
+    bool status = pb_decode_varint64(stream, x);
+    *x = (*x >> 1) ^ -(int64_t)(*x & 1);
+    return status;
+}
+
+bool pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    char bytes[8] = {0};
+    bool status = pb_read(stream, bytes, 8);
+    *(uint64_t*)dest =
+        (uint64_t)bytes[0] | ((uint64_t)bytes[1] << 8) |
+        ((uint64_t)bytes[2] << 16) | ((uint64_t)bytes[3] << 24) |
+        ((uint64_t)bytes[4] << 32) | ((uint64_t)bytes[5] << 40) |
+        ((uint64_t)bytes[6] << 48) | ((uint64_t)bytes[7] << 56);
+    return status;
+}
+
+bool pb_dec_bool(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint32_t temp = 0;
+    bool status = pb_decode_varint32(stream, &temp);
+    *(bool*)dest = !!temp;
+    return status;
+}
+
+bool pb_dec_float(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    return pb_read(stream, (char*)dest, sizeof(float));
+}
+
+bool pb_dec_double(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    return pb_read(stream, (char*)dest, sizeof(double));
+}
+
+bool pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    pb_bytearray_t *x = (pb_bytearray_t*)dest;
+    uint32_t temp;
+    if (!pb_decode_varint32(stream, &temp))
+        return false;
+    x->size = temp;
+    
+    if (x->size > field->fieldsize)
+        return false;
+    
+    return pb_read(stream, x->bytes, x->size);
+}
+
+bool pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint32_t size;
+    if (!pb_decode_varint32(stream, &size))
+        return false;
+    
+    if (size > field->fieldsize - 1)
+        return false;
+    
+    bool status = pb_read(stream, (char*)dest, size);
+    *((char*)dest + size) = 0;
+    return status;
+}
+
+bool pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    pb_callback_t *x = (pb_callback_t*)dest;
+    
+    if (x->funcs.decode == NULL)
+        return pb_skip_string(stream);
+    
+    uint32_t size;
+    if (!pb_decode_varint32(stream, &size))
+        return false;
+    
+    if (stream->bytes_left < size)
+        return false;
+    
+    // Make a limited-length istream for decoding submessage
+    pb_istream_t shortstream = *stream;
+    shortstream.bytes_left = size;
+    bool status = x->funcs.decode(&shortstream, field, x->arg);
+    stream->bytes_left -= size - shortstream.bytes_left;
+    return status;
+}