Diff: Nanopb/pb_decode.c

Revision:

0:d69efd0ee139

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Nanopb/pb_decode.c	Thu Sep 18 15:21:47 2014 +0000
@@ -0,0 +1,935 @@
+/* pb_decode.c -- decode a protobuf using minimal resources
+ *
+ * 2011 Petteri Aimonen <jpa@kapsi.fi>
+ */
+
+/* Use the GCC warn_unused_result attribute to check that all return values
+ * are propagated correctly. On other compilers and gcc before 3.4.0 just
+ * ignore the annotation.
+ */
+#if !defined(__GNUC__) || ( __GNUC__ < 3) || (__GNUC__ == 3 && __GNUC_MINOR__ < 4)
+    #define checkreturn
+#else
+    #define checkreturn __attribute__((warn_unused_result))
+#endif
+
+#define NANOPB_INTERNALS
+#include "pb.h"
+#include "pb_decode.h"
+
+/**************************************
+ * Declarations internal to this file *
+ **************************************/
+
+/* Iterator for pb_field_t list */
+typedef struct {
+    const pb_field_t *start; /* Start of the pb_field_t array */
+    const pb_field_t *pos; /* Current position of the iterator */
+    unsigned field_index; /* Zero-based index of the field. */
+    unsigned required_field_index; /* Zero-based index that counts only the required fields */
+    void *dest_struct; /* Pointer to the destination structure to decode to */
+    void *pData; /* Pointer where to store current field value */
+    void *pSize; /* Pointer where to store the size of current array field */
+} pb_field_iterator_t;
+
+typedef bool (*pb_decoder_t)(pb_istream_t *stream, const pb_field_t *field, void *dest) checkreturn;
+
+static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count);
+static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest);
+static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size);
+static void pb_field_init(pb_field_iterator_t *iter, const pb_field_t *fields, void *dest_struct);
+static bool pb_field_next(pb_field_iterator_t *iter);
+static bool checkreturn pb_field_find(pb_field_iterator_t *iter, uint32_t tag);
+static bool checkreturn decode_static_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter);
+static bool checkreturn decode_callback_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter);
+static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter);
+static bool checkreturn default_extension_decoder(pb_istream_t *stream, pb_extension_t *extension, uint32_t tag, pb_wire_type_t wire_type);
+static bool checkreturn decode_extension(pb_istream_t *stream, uint32_t tag, pb_wire_type_t wire_type, pb_field_iterator_t *iter);
+static bool checkreturn find_extension_field(pb_field_iterator_t *iter);
+static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct);
+static bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_uvarint(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_skip_varint(pb_istream_t *stream);
+static bool checkreturn pb_skip_string(pb_istream_t *stream);
+
+/* --- Function pointers to field decoders ---
+ * Order in the array must match pb_action_t LTYPE numbering.
+ */
+static const pb_decoder_t PB_DECODERS[PB_LTYPES_COUNT] = {
+    &pb_dec_varint,
+    &pb_dec_uvarint,
+    &pb_dec_svarint,
+    &pb_dec_fixed32,
+    &pb_dec_fixed64,
+    
+    &pb_dec_bytes,
+    &pb_dec_string,
+    &pb_dec_submessage,
+    NULL /* extensions */
+};
+
+/*******************************
+ * pb_istream_t implementation *
+ *******************************/
+
+static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count)
+{
+    uint8_t *source = (uint8_t*)stream->state;
+    stream->state = source + count;
+    
+    if (buf != NULL)
+    {
+        while (count--)
+            *buf++ = *source++;
+    }
+    
+    return true;
+}
+
+bool checkreturn pb_read(pb_istream_t *stream, uint8_t *buf, size_t count)
+{
+#ifndef PB_BUFFER_ONLY
+	if (buf == NULL && stream->callback != buf_read)
+	{
+		/* Skip input bytes */
+		uint8_t tmp[16];
+		while (count > 16)
+		{
+			if (!pb_read(stream, tmp, 16))
+				return false;
+			
+			count -= 16;
+		}
+		
+		return pb_read(stream, tmp, count);
+	}
+#endif
+
+    if (stream->bytes_left < count)
+        PB_RETURN_ERROR(stream, "end-of-stream");
+    
+#ifndef PB_BUFFER_ONLY
+    if (!stream->callback(stream, buf, count))
+        PB_RETURN_ERROR(stream, "io error");
+#else
+    if (!buf_read(stream, buf, count))
+        return false;
+#endif
+    
+    stream->bytes_left -= count;
+    return true;
+}
+
+/* Read a single byte from input stream. buf may not be NULL.
+ * This is an optimization for the varint decoding. */
+static bool checkreturn pb_readbyte(pb_istream_t *stream, uint8_t *buf)
+{
+    if (!stream->bytes_left)
+        PB_RETURN_ERROR(stream, "end-of-stream");
+
+#ifndef PB_BUFFER_ONLY
+    if (!stream->callback(stream, buf, 1))
+        PB_RETURN_ERROR(stream, "io error");
+#else
+    *buf = *(uint8_t*)stream->state;
+    stream->state = (uint8_t*)stream->state + 1;
+#endif
+
+    stream->bytes_left--;
+    
+    return true;    
+}
+
+pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
+{
+    pb_istream_t stream;
+#ifdef PB_BUFFER_ONLY
+    stream.callback = NULL;
+#else
+    stream.callback = &buf_read;
+#endif
+    stream.state = buf;
+    stream.bytes_left = bufsize;
+#ifndef PB_NO_ERRMSG
+    stream.errmsg = NULL;
+#endif
+    return stream;
+}
+
+/********************
+ * Helper functions *
+ ********************/
+
+static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
+{
+    uint8_t byte;
+    uint32_t result;
+    
+    if (!pb_readbyte(stream, &byte))
+        return false;
+    
+    if (!(byte & 0x80))
+    {
+        /* Quick case, 1 byte value */
+        result = byte;
+    }
+    else
+    {
+        /* Multibyte case */
+        uint8_t bitpos = 7;
+        result = byte & 0x7F;
+        
+        do
+        {
+            if (bitpos >= 32)
+                PB_RETURN_ERROR(stream, "varint overflow");
+            
+            if (!pb_readbyte(stream, &byte))
+                return false;
+            
+            result |= (uint32_t)(byte & 0x7F) << bitpos;
+            bitpos = (uint8_t)(bitpos + 7);
+        } while (byte & 0x80);
+   }
+   
+   *dest = result;
+   return true;
+}
+
+bool checkreturn pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
+{
+    uint8_t byte;
+    uint8_t bitpos = 0;
+    uint64_t result = 0;
+    
+    do
+    {
+        if (bitpos >= 64)
+            PB_RETURN_ERROR(stream, "varint overflow");
+        
+        if (!pb_readbyte(stream, &byte))
+            return false;
+
+        result |= (uint64_t)(byte & 0x7F) << bitpos;
+        bitpos = (uint8_t)(bitpos + 7);
+    } while (byte & 0x80);
+    
+    *dest = result;
+    return true;
+}
+
+bool checkreturn pb_skip_varint(pb_istream_t *stream)
+{
+    uint8_t byte;
+    do
+    {
+        if (!pb_read(stream, &byte, 1))
+            return false;
+    } while (byte & 0x80);
+    return true;
+}
+
+bool checkreturn 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 checkreturn pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof)
+{
+    uint32_t temp;
+    *eof = false;
+    *wire_type = (pb_wire_type_t) 0;
+    *tag = 0;
+    
+    if (!pb_decode_varint32(stream, &temp))
+    {
+        if (stream->bytes_left == 0)
+            *eof = true;
+
+        return false;
+    }
+    
+    if (temp == 0)
+    {
+        *eof = true; /* Special feature: allow 0-terminated messages. */
+        return false;
+    }
+    
+    *tag = temp >> 3;
+    *wire_type = (pb_wire_type_t)(temp & 7);
+    return true;
+}
+
+bool checkreturn pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type)
+{
+    switch (wire_type)
+    {
+        case PB_WT_VARINT: return pb_skip_varint(stream);
+        case PB_WT_64BIT: return pb_read(stream, NULL, 8);
+        case PB_WT_STRING: return pb_skip_string(stream);
+        case PB_WT_32BIT: return pb_read(stream, NULL, 4);
+        default: PB_RETURN_ERROR(stream, "invalid wire_type");
+    }
+}
+
+/* Read a raw value to buffer, for the purpose of passing it to callback as
+ * a substream. Size is maximum size on call, and actual size on return.
+ */
+static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
+{
+    size_t max_size = *size;
+    switch (wire_type)
+    {
+        case PB_WT_VARINT:
+            *size = 0;
+            do
+            {
+                (*size)++;
+                if (*size > max_size) return false;
+                if (!pb_read(stream, buf, 1)) return false;
+            } while (*buf++ & 0x80);
+            return true;
+            
+        case PB_WT_64BIT:
+            *size = 8;
+            return pb_read(stream, buf, 8);
+        
+        case PB_WT_32BIT:
+            *size = 4;
+            return pb_read(stream, buf, 4);
+        
+        default: PB_RETURN_ERROR(stream, "invalid wire_type");
+    }
+}
+
+/* Decode string length from stream and return a substream with limited length.
+ * Remember to close the substream using pb_close_string_substream().
+ */
+bool checkreturn pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
+{
+    uint32_t size;
+    if (!pb_decode_varint32(stream, &size))
+        return false;
+    
+    *substream = *stream;
+    if (substream->bytes_left < size)
+        PB_RETURN_ERROR(stream, "parent stream too short");
+    
+    substream->bytes_left = size;
+    stream->bytes_left -= size;
+    return true;
+}
+
+void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream)
+{
+    stream->state = substream->state;
+
+#ifndef PB_NO_ERRMSG
+    stream->errmsg = substream->errmsg;
+#endif
+}
+
+static void pb_field_init(pb_field_iterator_t *iter, const pb_field_t *fields, void *dest_struct)
+{
+    iter->start = iter->pos = fields;
+    iter->field_index = 0;
+    iter->required_field_index = 0;
+    iter->pData = (char*)dest_struct + iter->pos->data_offset;
+    iter->pSize = (char*)iter->pData + iter->pos->size_offset;
+    iter->dest_struct = dest_struct;
+}
+
+static bool pb_field_next(pb_field_iterator_t *iter)
+{
+    bool notwrapped = true;
+    size_t prev_size = iter->pos->data_size;
+    
+    if (PB_ATYPE(iter->pos->type) == PB_ATYPE_STATIC &&
+        PB_HTYPE(iter->pos->type) == PB_HTYPE_REPEATED)
+    {
+        prev_size *= iter->pos->array_size;
+    }
+    
+    if (iter->pos->tag == 0)
+        return false; /* Only happens with empty message types */
+    
+    if (PB_HTYPE(iter->pos->type) == PB_HTYPE_REQUIRED)
+        iter->required_field_index++;
+    
+    iter->pos++;
+    iter->field_index++;
+    if (iter->pos->tag == 0)
+    {
+        iter->pos = iter->start;
+        iter->field_index = 0;
+        iter->required_field_index = 0;
+        iter->pData = iter->dest_struct;
+        prev_size = 0;
+        notwrapped = false;
+    }
+    
+    iter->pData = (char*)iter->pData + prev_size + iter->pos->data_offset;
+    iter->pSize = (char*)iter->pData + iter->pos->size_offset;
+    return notwrapped;
+}
+
+static bool checkreturn pb_field_find(pb_field_iterator_t *iter, uint32_t tag)
+{
+    unsigned start = iter->field_index;
+    
+    do {
+        if (iter->pos->tag == tag &&
+            PB_LTYPE(iter->pos->type) != PB_LTYPE_EXTENSION)
+        {
+            return true;
+        }
+        pb_field_next(iter);
+    } while (iter->field_index != start);
+    
+    return false;
+}
+
+/*************************
+ * Decode a single field *
+ *************************/
+
+static bool checkreturn decode_static_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter)
+{
+    pb_type_t type;
+    pb_decoder_t func;
+    
+    type = iter->pos->type;
+    func = PB_DECODERS[PB_LTYPE(type)];
+
+    switch (PB_HTYPE(type))
+    {
+        case PB_HTYPE_REQUIRED:
+            return func(stream, iter->pos, iter->pData);
+            
+        case PB_HTYPE_OPTIONAL:
+            *(bool*)iter->pSize = true;
+            return func(stream, iter->pos, iter->pData);
+    
+        case PB_HTYPE_REPEATED:
+            if (wire_type == PB_WT_STRING
+                && PB_LTYPE(type) <= PB_LTYPE_LAST_PACKABLE)
+            {
+                /* Packed array */
+                bool status = true;
+                size_t *size = (size_t*)iter->pSize;
+                pb_istream_t substream;
+                if (!pb_make_string_substream(stream, &substream))
+                    return false;
+                
+                while (substream.bytes_left && *size < iter->pos->array_size)
+                {
+                    void *pItem = (uint8_t*)iter->pData + iter->pos->data_size * (*size);
+                    if (!func(&substream, iter->pos, pItem))
+                    {
+                        status = false;
+                        break;
+                    }
+                    (*size)++;
+                }
+                pb_close_string_substream(stream, &substream);
+                
+                if (substream.bytes_left != 0)
+                    PB_RETURN_ERROR(stream, "array overflow");
+                
+                return status;
+            }
+            else
+            {
+                /* Repeated field */
+                size_t *size = (size_t*)iter->pSize;
+                void *pItem = (uint8_t*)iter->pData + iter->pos->data_size * (*size);
+                if (*size >= iter->pos->array_size)
+                    PB_RETURN_ERROR(stream, "array overflow");
+                
+                (*size)++;
+                return func(stream, iter->pos, pItem);
+            }
+
+        default:
+            PB_RETURN_ERROR(stream, "invalid field type");
+    }
+}
+
+static bool checkreturn decode_callback_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter)
+{
+    pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
+    
+#ifdef PB_OLD_CALLBACK_STYLE
+    void *arg = pCallback->arg;
+#else
+    void **arg = &(pCallback->arg);
+#endif
+    
+    if (pCallback->funcs.decode == NULL)
+        return pb_skip_field(stream, wire_type);
+    
+    if (wire_type == PB_WT_STRING)
+    {
+        pb_istream_t substream;
+        
+        if (!pb_make_string_substream(stream, &substream))
+            return false;
+        
+        do
+        {
+            if (!pCallback->funcs.decode(&substream, iter->pos, arg))
+                PB_RETURN_ERROR(stream, "callback failed");
+        } while (substream.bytes_left);
+        
+        pb_close_string_substream(stream, &substream);
+        return true;
+    }
+    else
+    {
+        /* Copy the single scalar value to stack.
+         * This is required so that we can limit the stream length,
+         * which in turn allows to use same callback for packed and
+         * not-packed fields. */
+        pb_istream_t substream;
+        uint8_t buffer[10];
+        size_t size = sizeof(buffer);
+        
+        if (!read_raw_value(stream, wire_type, buffer, &size))
+            return false;
+        substream = pb_istream_from_buffer(buffer, size);
+        
+        return pCallback->funcs.decode(&substream, iter->pos, arg);
+    }
+}
+
+static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter)
+{
+    switch (PB_ATYPE(iter->pos->type))
+    {
+        case PB_ATYPE_STATIC:
+            return decode_static_field(stream, wire_type, iter);
+        
+        case PB_ATYPE_CALLBACK:
+            return decode_callback_field(stream, wire_type, iter);
+        
+        default:
+            PB_RETURN_ERROR(stream, "invalid field type");
+    }
+}
+
+/* Default handler for extension fields. Expects a pb_field_t structure
+ * in extension->type->arg. */
+static bool checkreturn default_extension_decoder(pb_istream_t *stream,
+    pb_extension_t *extension, uint32_t tag, pb_wire_type_t wire_type)
+{
+    const pb_field_t *field = (const pb_field_t*)extension->type->arg;
+    pb_field_iterator_t iter;
+    bool dummy;
+    
+    if (field->tag != tag)
+        return true;
+    
+    iter.start = field;
+    iter.pos = field;
+    iter.field_index = 0;
+    iter.required_field_index = 0;
+    iter.dest_struct = extension->dest;
+    iter.pData = extension->dest;
+    iter.pSize = &dummy;
+    
+    return decode_field(stream, wire_type, &iter);
+}
+
+/* Try to decode an unknown field as an extension field. Tries each extension
+ * decoder in turn, until one of them handles the field or loop ends. */
+static bool checkreturn decode_extension(pb_istream_t *stream,
+    uint32_t tag, pb_wire_type_t wire_type, pb_field_iterator_t *iter)
+{
+    pb_extension_t *extension = *(pb_extension_t* const *)iter->pData;
+    size_t pos = stream->bytes_left;
+    
+    while (extension && pos == stream->bytes_left)
+    {
+        bool status;
+        if (extension->type->decode)
+            status = extension->type->decode(stream, extension, tag, wire_type);
+        else
+            status = default_extension_decoder(stream, extension, tag, wire_type);
+
+        if (!status)
+            return false;
+        
+        extension = extension->next;
+    }
+    
+    return true;
+}
+
+/* Step through the iterator until an extension field is found or until all
+ * entries have been checked. There can be only one extension field per
+ * message. Returns false if no extension field is found. */
+static bool checkreturn find_extension_field(pb_field_iterator_t *iter)
+{
+    unsigned start = iter->field_index;
+    
+    do {
+        if (PB_LTYPE(iter->pos->type) == PB_LTYPE_EXTENSION)
+            return true;
+        pb_field_next(iter);
+    } while (iter->field_index != start);
+    
+    return false;
+}
+
+/* Initialize message fields to default values, recursively */
+static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct)
+{
+    pb_field_iterator_t iter;
+    pb_field_init(&iter, fields, dest_struct);
+    
+    /* Initialize size/has fields and apply default values */
+    do
+    {
+        pb_type_t type;
+        type = iter.pos->type;
+    
+        if (iter.pos->tag == 0)
+            continue;
+        
+        if (PB_ATYPE(type) == PB_ATYPE_STATIC)
+        {
+            /* Initialize the size field for optional/repeated fields to 0. */
+            if (PB_HTYPE(type) == PB_HTYPE_OPTIONAL)
+            {
+                *(bool*)iter.pSize = false;
+            }
+            else if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
+            {
+                *(size_t*)iter.pSize = 0;
+                continue; /* Array is empty, no need to initialize contents */
+            }
+            
+            /* Initialize field contents to default value */
+            if (PB_LTYPE(iter.pos->type) == PB_LTYPE_SUBMESSAGE)
+            {
+                pb_message_set_to_defaults((const pb_field_t *) iter.pos->ptr, iter.pData);
+            }
+            else if (iter.pos->ptr != NULL)
+            {
+                memcpy(iter.pData, iter.pos->ptr, iter.pos->data_size);
+            }
+            else
+            {
+                memset(iter.pData, 0, iter.pos->data_size);
+            }
+        }
+        else if (PB_ATYPE(type) == PB_ATYPE_CALLBACK)
+        {
+            continue; /* Don't overwrite callback */
+        }
+    } while (pb_field_next(&iter));
+}
+
+/*********************
+ * Decode all fields *
+ *********************/
+
+bool checkreturn pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
+{
+    uint8_t fields_seen[(PB_MAX_REQUIRED_FIELDS + 7) / 8] = {0}; /* Used to check for required fields */
+    uint32_t extension_range_start = 0;
+    pb_field_iterator_t iter;
+    
+    pb_field_init(&iter, fields, dest_struct);
+    
+    while (stream->bytes_left)
+    {
+        uint32_t tag;
+        pb_wire_type_t wire_type;
+        bool eof;
+        
+        if (!pb_decode_tag(stream, &wire_type, &tag, &eof))
+        {
+            if (eof)
+                break;
+            else
+                return false;
+        }
+        
+        if (!pb_field_find(&iter, tag))
+        {
+            /* No match found, check if it matches an extension. */
+            if (tag >= extension_range_start)
+            {
+                if (!find_extension_field(&iter))
+                    extension_range_start = (uint32_t)-1;
+                else
+                    extension_range_start = iter.pos->tag;
+                
+                if (tag >= extension_range_start)
+                {
+                    size_t pos = stream->bytes_left;
+                
+                    if (!decode_extension(stream, tag, wire_type, &iter))
+                        return false;
+                    
+                    if (pos != stream->bytes_left)
+                    {
+                        /* The field was handled */
+                        continue;                    
+                    }
+                }
+            }
+        
+            /* No match found, skip data */
+            if (!pb_skip_field(stream, wire_type))
+                return false;
+            continue;
+        }
+        
+        if (PB_HTYPE(iter.pos->type) == PB_HTYPE_REQUIRED
+            && iter.required_field_index < PB_MAX_REQUIRED_FIELDS)
+        {
+            fields_seen[iter.required_field_index >> 3] |= (uint8_t)(1 << (iter.required_field_index & 7));
+        }
+            
+        if (!decode_field(stream, wire_type, &iter))
+            return false;
+    }
+    
+    /* Check that all required fields were present. */
+    {
+        /* First figure out the number of required fields by
+         * seeking to the end of the field array. Usually we
+         * are already close to end after decoding.
+         */
+        unsigned req_field_count;
+        pb_type_t last_type;
+        unsigned i;
+        do {
+            req_field_count = iter.required_field_index;
+            last_type = iter.pos->type;
+        } while (pb_field_next(&iter));
+        
+        /* Fixup if last field was also required. */
+        if (PB_HTYPE(last_type) == PB_HTYPE_REQUIRED && iter.pos->tag)
+            req_field_count++;
+        
+        /* Check the whole bytes */
+        for (i = 0; i < (req_field_count >> 3); i++)
+        {
+            if (fields_seen[i] != 0xFF)
+                PB_RETURN_ERROR(stream, "missing required field");
+        }
+        
+        /* Check the remaining bits */
+        if (fields_seen[req_field_count >> 3] != (0xFF >> (8 - (req_field_count & 7))))
+            PB_RETURN_ERROR(stream, "missing required field");
+    }
+    
+    return true;
+}
+
+bool checkreturn pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
+{
+    pb_message_set_to_defaults(fields, dest_struct);
+    return pb_decode_noinit(stream, fields, dest_struct);
+}
+
+bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
+{
+    pb_istream_t substream;
+    bool status;
+    
+    if (!pb_make_string_substream(stream, &substream))
+        return false;
+    
+    status = pb_decode(&substream, fields, dest_struct);
+    pb_close_string_substream(stream, &substream);
+    return status;
+}
+
+/* Field decoders */
+
+bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest)
+{
+    uint64_t value;
+    if (!pb_decode_varint(stream, &value))
+        return false;
+    
+    if (value & 1)
+        *dest = (int64_t)(~(value >> 1));
+    else
+        *dest = (int64_t)(value >> 1);
+    
+    return true;
+}
+
+bool pb_decode_fixed32(pb_istream_t *stream, void *dest)
+{
+    #ifdef __BIG_ENDIAN__
+    uint8_t *bytes = (uint8_t*)dest;
+    uint8_t lebytes[4];
+    
+    if (!pb_read(stream, lebytes, 4))
+        return false;
+    
+    bytes[0] = lebytes[3];
+    bytes[1] = lebytes[2];
+    bytes[2] = lebytes[1];
+    bytes[3] = lebytes[0];
+    return true;
+    #else
+    return pb_read(stream, (uint8_t*)dest, 4);
+    #endif   
+}
+
+bool pb_decode_fixed64(pb_istream_t *stream, void *dest)
+{
+    #ifdef __BIG_ENDIAN__
+    uint8_t *bytes = (uint8_t*)dest;
+    uint8_t lebytes[8];
+    
+    if (!pb_read(stream, lebytes, 8))
+        return false;
+    
+    bytes[0] = lebytes[7];
+    bytes[1] = lebytes[6];
+    bytes[2] = lebytes[5];
+    bytes[3] = lebytes[4];
+    bytes[4] = lebytes[3];
+    bytes[5] = lebytes[2];
+    bytes[6] = lebytes[1];
+    bytes[7] = lebytes[0];
+    return true;
+    #else
+    return pb_read(stream, (uint8_t*)dest, 8);
+    #endif   
+}
+
+bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint64_t value;
+    if (!pb_decode_varint(stream, &value))
+        return false;
+    
+    switch (field->data_size)
+    {
+        case 1: *(int8_t*)dest = (int8_t)value; break;
+        case 2: *(int16_t*)dest = (int16_t)value; break;
+        case 4: *(int32_t*)dest = (int32_t)value; break;
+        case 8: *(int64_t*)dest = (int64_t)value; break;
+        default: PB_RETURN_ERROR(stream, "invalid data_size");
+    }
+    
+    return true;
+}
+
+bool checkreturn pb_dec_uvarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint64_t value;
+    if (!pb_decode_varint(stream, &value))
+        return false;
+    
+    switch (field->data_size)
+    {
+        case 4: *(uint32_t*)dest = (uint32_t)value; break;
+        case 8: *(uint64_t*)dest = value; break;
+        default: PB_RETURN_ERROR(stream, "invalid data_size");
+    }
+    
+    return true;
+}
+
+bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    int64_t value;
+    if (!pb_decode_svarint(stream, &value))
+        return false;
+    
+    switch (field->data_size)
+    {
+        case 4: *(int32_t*)dest = (int32_t)value; break;
+        case 8: *(int64_t*)dest = value; break;
+        default: PB_RETURN_ERROR(stream, "invalid data_size");
+    }
+    
+    return true;
+}
+
+bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    UNUSED(field);
+    return pb_decode_fixed32(stream, dest);
+}
+
+bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    UNUSED(field);
+    return pb_decode_fixed64(stream, dest);
+}
+
+bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    pb_bytes_array_t *x = (pb_bytes_array_t*)dest;
+    
+    uint32_t temp;
+    if (!pb_decode_varint32(stream, &temp))
+        return false;
+    x->size = temp;
+    
+    /* Check length, noting the space taken by the size_t header. */
+    if (x->size > field->data_size - offsetof(pb_bytes_array_t, bytes))
+        PB_RETURN_ERROR(stream, "bytes overflow");
+    
+    return pb_read(stream, x->bytes, x->size);
+}
+
+bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint32_t size;
+    bool status;
+    if (!pb_decode_varint32(stream, &size))
+        return false;
+    
+    /* Check length, noting the null terminator */
+    if (size + 1 > field->data_size)
+        PB_RETURN_ERROR(stream, "string overflow");
+    
+    status = pb_read(stream, (uint8_t*)dest, size);
+    *((uint8_t*)dest + size) = 0;
+    return status;
+}
+
+bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    bool status;
+    pb_istream_t substream;
+    const pb_field_t* submsg_fields = (const pb_field_t*)field->ptr;
+    
+    if (!pb_make_string_substream(stream, &substream))
+        return false;
+    
+    if (field->ptr == NULL)
+        PB_RETURN_ERROR(stream, "invalid field descriptor");
+    
+    /* New array entries need to be initialized, while required and optional
+     * submessages have already been initialized in the top-level pb_decode. */
+    if (PB_HTYPE(field->type) == PB_HTYPE_REPEATED)
+        status = pb_decode(&substream, submsg_fields, dest);
+    else
+        status = pb_decode_noinit(&substream, submsg_fields, dest);
+    
+    pb_close_string_substream(stream, &substream);
+    return status;
+}