Encoder

git-svn-id: https://svn.kapsi.fi/jpa/nanopb@951 e3a754e5-d11d-0410-8d38-ebb782a927b9

1 files changed, 326 insertions, 0 deletions

diff --git a/pb_encode.c b/pb_encode.c
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--- /dev/null
+++ b/pb_encode.c
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+/* pb_encode.c -- encode a protobuf using minimal resources
+ *
+ * 2011 Petteri Aimonen <jpa@kapsi.fi>
+ */
+
+#include "pb.h"
+#include "pb_encode.h"
+#include <string.h>
+
+typedef bool (*pb_encoder_t)(pb_ostream_t *stream, const pb_field_t *field, const void *src);
+
+/* --- Function pointers to field encoders ---
+ * Order in the array must match pb_action_t LTYPE numbering.
+ */
+static const pb_encoder_t PB_ENCODERS[PB_LTYPES_COUNT] = {
+    &pb_enc_varint,
+    &pb_enc_svarint,
+    &pb_enc_fixed,
+    
+    &pb_enc_bytes,
+    &pb_enc_string,
+    &pb_enc_submessage
+};
+
+/* pb_ostream_t implementation */
+
+static bool buf_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
+{
+    uint8_t *dest = (uint8_t*)stream->state;
+    memcpy(dest, buf, count);
+    stream->state = dest + count;
+    return true;
+}
+
+pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize)
+{
+    pb_ostream_t stream;
+    stream.callback = &buf_write;
+    stream.state = buf;
+    stream.max_size = bufsize;
+    stream.bytes_written = 0;
+    return stream;
+}
+
+bool pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
+{
+    stream->bytes_written += count;
+    
+    if (stream->callback == NULL)
+        return true;
+    
+    if (stream->bytes_written > stream->max_size)
+        return false;
+    
+    return stream->callback(stream, buf, count);
+}
+
+/* Main encoding stuff */
+
+static bool encode_array(pb_ostream_t *stream, const pb_field_t *field,
+                         const void *pData, size_t count, pb_encoder_t func)
+{
+    int i;
+    const void *p;
+    size_t size;
+    
+    if (PB_LTYPE(field->type) < PB_LTYPE_LAST_PACKABLE)
+    {
+        if (!pb_encode_tag(stream, PB_WT_STRING, field->tag))
+            return false;
+        
+        /* Determine the total size of packed array. */
+        if (PB_LTYPE(field->type) == PB_LTYPE_FIXED)
+        {
+            size = field->data_size * count;
+        }
+        else
+        {
+            pb_ostream_t sizestream = {0};
+            p = pData;
+            for (i = 0; i < count; i++)
+            {
+                if (!func(&sizestream, field, p))
+                    return false;
+                p = (const char*)p + field->data_size;
+            }
+            size = sizestream.bytes_written;
+        }
+        
+        pb_encode_varint(stream, size);
+        
+        if (stream->callback == NULL)
+            return pb_write(stream, NULL, size); /* Just sizing.. */
+        
+        /* Write the data */
+        p = pData;
+        for (i = 0; i < count; i++)
+        {
+            if (!func(stream, field, p))
+                return false;
+            p = (const char*)p + field->data_size;
+        }
+    }
+    else
+    {
+        p = pData;
+        for (i = 0; i < count; i++)
+        {
+            if (!pb_encode_tag_for_field(stream, field))
+                return false;
+            if (!func(stream, field, p))
+                return false;
+            p = (const char*)p + field->data_size;
+        }
+    }
+    
+    return true;
+}
+
+bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
+{
+    const pb_field_t *field = fields;
+    const void *pData = src_struct;
+    const void *pSize;
+    
+    while (field->tag != 0)
+    {
+        pData = (const char*)pData + field->data_offset;
+        pSize = (const char*)pData + field->size_offset;
+        
+        pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
+        
+        switch (PB_HTYPE(field->type))
+        {
+            case PB_HTYPE_REQUIRED:
+                if (!pb_encode_tag_for_field(stream, field))
+                    return false;
+                if (!func(stream, field, pData))
+                    return false;
+                break;
+            
+            case PB_HTYPE_OPTIONAL:
+                if (*(bool*)pSize)
+                {
+                    if (!pb_encode_tag_for_field(stream, field))
+                        return false;
+                
+                    if (!func(stream, field, pData))
+                        return false;
+                }
+                break;
+            
+            case PB_HTYPE_ARRAY:
+                if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
+                    return false;
+                break;
+            
+            case PB_HTYPE_CALLBACK:
+            {
+                pb_callback_t *callback = (pb_callback_t*)pData;
+                if (callback->funcs.encode != NULL)
+                {
+                    if (!callback->funcs.encode(stream, field, callback->arg))
+                        return false;
+                }
+                break;
+            }
+        }
+    
+        field++;
+    }
+    
+    return true;
+}
+
+/* Helper functions */
+bool pb_encode_varint(pb_ostream_t *stream, uint64_t value)
+{
+    uint8_t buffer[10];
+    int i = 0;
+    
+    if (value == 0)
+        return pb_write(stream, (uint8_t*)&value, 1);
+    
+    while (value)
+    {
+        buffer[i] = (value & 0x7F) | 0x80;
+        value >>= 7;
+        i++;
+    }
+    buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
+    
+    return pb_write(stream, buffer, i);
+}
+
+bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
+{
+    int tag = wiretype | (field_number << 3);
+    return pb_encode_varint(stream, tag);
+}
+
+bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
+{
+    pb_wire_type_t wiretype;
+    switch (PB_LTYPE(field->type))
+    {
+        case PB_LTYPE_VARINT:
+        case PB_LTYPE_SVARINT:
+            wiretype = PB_WT_VARINT;
+            break;
+        
+        case PB_LTYPE_FIXED:
+            if (field->data_size == 4)
+                wiretype = PB_WT_32BIT;
+            else if (field->data_size == 8)
+                wiretype = PB_WT_64BIT;
+            else
+                return false;
+            break;
+        
+        case PB_LTYPE_BYTES:
+        case PB_LTYPE_STRING:
+        case PB_LTYPE_SUBMESSAGE:
+            wiretype = PB_WT_STRING;
+            break;
+        
+        default:
+            return false;
+    }
+    
+    return pb_encode_tag(stream, wiretype, field->tag);
+}
+
+bool pb_encode_string(pb_ostream_t *stream, uint8_t *buffer, size_t size)
+{
+    if (!pb_encode_varint(stream, size))
+        return false;
+    
+    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)
+{
+#ifdef __BIG_ENDIAN__
+    memcpy((char*)dest + (destsize - srcsize), src, srcsize);
+#else
+    memcpy(dest, src, srcsize);
+#endif
+}
+
+bool 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);
+    return pb_encode_varint(stream, value);
+}
+
+bool pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
+{
+    uint64_t value = 0;
+    uint64_t zigzagged;
+    uint64_t mask;
+    endian_copy(&value, src, sizeof(value), field->data_size);
+    
+    mask = 0x80 << (field->data_size * 8);
+    zigzagged = (value & ~mask) << 1;
+    if (value & mask) zigzagged |= 1;
+    
+    return pb_encode_varint(stream, value);
+}
+
+bool pb_enc_fixed(pb_ostream_t *stream, const pb_field_t *field, const void *src)
+{
+    #ifdef __BIG_ENDIAN__
+    uint8_t bytes[8] = {0};
+    endian_copy(bytes, src, sizeof(bytes), field->data_size);
+    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, field->data_size);
+    #else
+    return pb_write(stream, (uint8_t*)src, field->data_size);
+    #endif
+}
+
+bool pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
+{
+    pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
+    return pb_encode_string(stream, bytes->bytes, bytes->size);
+}
+
+bool pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
+{
+    return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
+}
+
+bool pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
+{
+    pb_ostream_t sizestream = {0};
+    size_t size;
+    
+    if (field->ptr == NULL)
+        return false;
+    
+    if (!pb_encode(&sizestream, (pb_field_t*)field->ptr, src))
+        return false;
+    
+    size = sizestream.bytes_written;
+    
+    if (!pb_encode_varint(stream, size))
+        return false;
+    
+    if (stream->callback == NULL)
+        return pb_write(stream, NULL, size); /* Just sizing */
+    
+    return pb_encode(stream, (pb_field_t*)field->ptr, src);
+}
+