pb_encode.c

00001 /* pb_encode.c -- encode a protobuf using minimal resources
00002  *
00003  * 2011 Petteri Aimonen <jpa@kapsi.fi>
00004  */
00005 
00006 #include "pb.h"
00007 #include "pb_encode.h"
00008 #include "pb_common.h"
00009 
00010 /* Use the GCC warn_unused_result attribute to check that all return values
00011  * are propagated correctly. On other compilers and gcc before 3.4.0 just
00012  * ignore the annotation.
00013  */
00014 #if !defined(__GNUC__) || ( __GNUC__ < 3) || (__GNUC__ == 3 && __GNUC_MINOR__ < 4)
00015     #define checkreturn
00016 #else
00017     #define checkreturn __attribute__((warn_unused_result))
00018 #endif
00019 
00020 /**************************************
00021  * Declarations internal to this file *
00022  **************************************/
00023 typedef bool (*pb_encoder_t)(pb_ostream_t *stream, const pb_field_t *field, const void *src) checkreturn;
00024 
00025 static bool checkreturn buf_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
00026 static bool checkreturn encode_array(pb_ostream_t *stream, const pb_field_t *field, const void *pData, size_t count, pb_encoder_t func);
00027 static bool checkreturn encode_field(pb_ostream_t *stream, const pb_field_t *field, const void *pData);
00028 static bool checkreturn default_extension_encoder(pb_ostream_t *stream, const pb_extension_t *extension);
00029 static bool checkreturn encode_extension_field(pb_ostream_t *stream, const pb_field_t *field, const void *pData);
00030 static bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00031 static bool checkreturn pb_enc_uvarint(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00032 static bool checkreturn pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00033 static bool checkreturn pb_enc_fixed32(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00034 static bool checkreturn pb_enc_fixed64(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00035 static bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00036 static bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00037 static bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src);
00038 
00039 /* --- Function pointers to field encoders ---
00040  * Order in the array must match pb_action_t LTYPE numbering.
00041  */
00042 static const pb_encoder_t PB_ENCODERS[PB_LTYPES_COUNT] = {
00043     &pb_enc_varint,
00044     &pb_enc_uvarint,
00045     &pb_enc_svarint,
00046     &pb_enc_fixed32,
00047     &pb_enc_fixed64,
00048     
00049     &pb_enc_bytes,
00050     &pb_enc_string,
00051     &pb_enc_submessage,
00052     NULL /* extensions */
00053 };
00054 
00055 /*******************************
00056  * pb_ostream_t implementation *
00057  *******************************/
00058 
00059 static bool checkreturn buf_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count)
00060 {
00061     pb_byte_t *dest = (pb_byte_t*)stream->state;
00062     stream->state = dest + count;
00063     
00064     while (count--)
00065         *dest++ = *buf++;
00066     
00067     return true;
00068 }
00069 
00070 pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize)
00071 {
00072     pb_ostream_t stream;
00073 #ifdef PB_BUFFER_ONLY
00074     stream.callback = (void*)1; /* Just a marker value */
00075 #else
00076     stream.callback = &buf_write;
00077 #endif
00078     stream.state = buf;
00079     stream.max_size = bufsize;
00080     stream.bytes_written = 0;
00081 #ifndef PB_NO_ERRMSG
00082     stream.errmsg = NULL;
00083 #endif
00084     return stream;
00085 }
00086 
00087 bool checkreturn pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count)
00088 {
00089     if (stream->callback != NULL)
00090     {
00091         if (stream->bytes_written + count > stream->max_size)
00092             PB_RETURN_ERROR(stream, "stream full");
00093 
00094 #ifdef PB_BUFFER_ONLY
00095         if (!buf_write(stream, buf, count))
00096             PB_RETURN_ERROR(stream, "io error");
00097 #else        
00098         if (!stream->callback(stream, buf, count))
00099             PB_RETURN_ERROR(stream, "io error");
00100 #endif
00101     }
00102     
00103     stream->bytes_written += count;
00104     return true;
00105 }
00106 
00107 /*************************
00108  * Encode a single field *
00109  *************************/
00110 
00111 /* Encode a static array. Handles the size calculations and possible packing. */
00112 static bool checkreturn encode_array(pb_ostream_t *stream, const pb_field_t *field,
00113                          const void *pData, size_t count, pb_encoder_t func)
00114 {
00115     size_t i;
00116     const void *p;
00117     size_t size;
00118     
00119     if (count == 0)
00120         return true;
00121 
00122     if (PB_ATYPE(field->type) != PB_ATYPE_POINTER && count > field->array_size)
00123         PB_RETURN_ERROR(stream, "array max size exceeded");
00124     
00125     /* We always pack arrays if the datatype allows it. */
00126     if (PB_LTYPE(field->type) <= PB_LTYPE_LAST_PACKABLE)
00127     {
00128         if (!pb_encode_tag(stream, PB_WT_STRING, field->tag))
00129             return false;
00130         
00131         /* Determine the total size of packed array. */
00132         if (PB_LTYPE(field->type) == PB_LTYPE_FIXED32)
00133         {
00134             size = 4 * count;
00135         }
00136         else if (PB_LTYPE(field->type) == PB_LTYPE_FIXED64)
00137         {
00138             size = 8 * count;
00139         }
00140         else
00141         { 
00142             pb_ostream_t sizestream = PB_OSTREAM_SIZING;
00143             p = pData;
00144             for (i = 0; i < count; i++)
00145             {
00146                 if (!func(&sizestream, field, p))
00147                     return false;
00148                 p = (const char*)p + field->data_size;
00149             }
00150             size = sizestream.bytes_written;
00151         }
00152         
00153         if (!pb_encode_varint(stream, (uint64_t)size))
00154             return false;
00155         
00156         if (stream->callback == NULL)
00157             return pb_write(stream, NULL, size); /* Just sizing.. */
00158         
00159         /* Write the data */
00160         p = pData;
00161         for (i = 0; i < count; i++)
00162         {
00163             if (!func(stream, field, p))
00164                 return false;
00165             p = (const char*)p + field->data_size;
00166         }
00167     }
00168     else
00169     {
00170         p = pData;
00171         for (i = 0; i < count; i++)
00172         {
00173             if (!pb_encode_tag_for_field(stream, field))
00174                 return false;
00175 
00176             /* Normally the data is stored directly in the array entries, but
00177              * for pointer-type string and bytes fields, the array entries are
00178              * actually pointers themselves also. So we have to dereference once
00179              * more to get to the actual data. */
00180             if (PB_ATYPE(field->type) == PB_ATYPE_POINTER &&
00181                 (PB_LTYPE(field->type) == PB_LTYPE_STRING ||
00182                  PB_LTYPE(field->type) == PB_LTYPE_BYTES))
00183             {
00184                 if (!func(stream, field, *(const void* const*)p))
00185                     return false;      
00186             }
00187             else
00188             {
00189                 if (!func(stream, field, p))
00190                     return false;
00191             }
00192             p = (const char*)p + field->data_size;
00193         }
00194     }
00195     
00196     return true;
00197 }
00198 
00199 /* Encode a field with static or pointer allocation, i.e. one whose data
00200  * is available to the encoder directly. */
00201 static bool checkreturn encode_basic_field(pb_ostream_t *stream,
00202     const pb_field_t *field, const void *pData)
00203 {
00204     pb_encoder_t func;
00205     const void *pSize;
00206     bool implicit_has = true;
00207     
00208     func = PB_ENCODERS[PB_LTYPE(field->type)];
00209     
00210     if (field->size_offset)
00211         pSize = (const char*)pData + field->size_offset;
00212     else
00213         pSize = &implicit_has;
00214 
00215     if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
00216     {
00217         /* pData is a pointer to the field, which contains pointer to
00218          * the data. If the 2nd pointer is NULL, it is interpreted as if
00219          * the has_field was false.
00220          */
00221         
00222         pData = *(const void* const*)pData;
00223         implicit_has = (pData != NULL);
00224     }
00225 
00226     switch (PB_HTYPE(field->type))
00227     {
00228         case PB_HTYPE_REQUIRED:
00229             if (!pData)
00230                 PB_RETURN_ERROR(stream, "missing required field");
00231             if (!pb_encode_tag_for_field(stream, field))
00232                 return false;
00233             if (!func(stream, field, pData))
00234                 return false;
00235             break;
00236         
00237         case PB_HTYPE_OPTIONAL:
00238             if (*(const bool*)pSize)
00239             {
00240                 if (!pb_encode_tag_for_field(stream, field))
00241                     return false;
00242             
00243                 if (!func(stream, field, pData))
00244                     return false;
00245             }
00246             break;
00247         
00248         case PB_HTYPE_REPEATED:
00249             if (!encode_array(stream, field, pData, *(const pb_size_t*)pSize, func))
00250                 return false;
00251             break;
00252         
00253         case PB_HTYPE_ONEOF:
00254             if (*(const pb_size_t*)pSize == field->tag)
00255             {
00256                 if (!pb_encode_tag_for_field(stream, field))
00257                     return false;
00258 
00259                 if (!func(stream, field, pData))
00260                     return false;
00261             }
00262             break;
00263             
00264         default:
00265             PB_RETURN_ERROR(stream, "invalid field type");
00266     }
00267     
00268     return true;
00269 }
00270 
00271 /* Encode a field with callback semantics. This means that a user function is
00272  * called to provide and encode the actual data. */
00273 static bool checkreturn encode_callback_field(pb_ostream_t *stream,
00274     const pb_field_t *field, const void *pData)
00275 {
00276     const pb_callback_t *callback = (const pb_callback_t*)pData;
00277     
00278 #ifdef PB_OLD_CALLBACK_STYLE
00279     const void *arg = callback->arg;
00280 #else
00281     void * const *arg = &(callback->arg);
00282 #endif    
00283     
00284     if (callback->funcs.encode != NULL)
00285     {
00286         if (!callback->funcs.encode(stream, field, arg))
00287             PB_RETURN_ERROR(stream, "callback error");
00288     }
00289     return true;
00290 }
00291 
00292 /* Encode a single field of any callback or static type. */
00293 static bool checkreturn encode_field(pb_ostream_t *stream,
00294     const pb_field_t *field, const void *pData)
00295 {
00296     switch (PB_ATYPE(field->type))
00297     {
00298         case PB_ATYPE_STATIC:
00299         case PB_ATYPE_POINTER:
00300             return encode_basic_field(stream, field, pData);
00301         
00302         case PB_ATYPE_CALLBACK:
00303             return encode_callback_field(stream, field, pData);
00304         
00305         default:
00306             PB_RETURN_ERROR(stream, "invalid field type");
00307     }
00308 }
00309 
00310 /* Default handler for extension fields. Expects to have a pb_field_t
00311  * pointer in the extension->type->arg field. */
00312 static bool checkreturn default_extension_encoder(pb_ostream_t *stream,
00313     const pb_extension_t *extension)
00314 {
00315     const pb_field_t *field = (const pb_field_t*)extension->type->arg;
00316     
00317     if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
00318     {
00319         /* For pointer extensions, the pointer is stored directly
00320          * in the extension structure. This avoids having an extra
00321          * indirection. */
00322         return encode_field(stream, field, &extension->dest);
00323     }
00324     else
00325     {
00326         return encode_field(stream, field, extension->dest);
00327     }
00328 }
00329 
00330 /* Walk through all the registered extensions and give them a chance
00331  * to encode themselves. */
00332 static bool checkreturn encode_extension_field(pb_ostream_t *stream,
00333     const pb_field_t *field, const void *pData)
00334 {
00335     const pb_extension_t *extension = *(const pb_extension_t* const *)pData;
00336     PB_UNUSED(field);
00337     
00338     while (extension)
00339     {
00340         bool status;
00341         if (extension->type->encode)
00342             status = extension->type->encode(stream, extension);
00343         else
00344             status = default_extension_encoder(stream, extension);
00345 
00346         if (!status)
00347             return false;
00348         
00349         extension = extension->next;
00350     }
00351     
00352     return true;
00353 }
00354 
00355 /*********************
00356  * Encode all fields *
00357  *********************/
00358 
00359 static void *remove_const(const void *p)
00360 {
00361     /* Note: this casts away const, in order to use the common field iterator
00362      * logic for both encoding and decoding. */
00363     union {
00364         void *p1;
00365         const void *p2;
00366     } t;
00367     t.p2 = p;
00368     return t.p1;
00369 }
00370 
00371 bool checkreturn pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
00372 {
00373     pb_field_iter_t iter;
00374     if (!pb_field_iter_begin(&iter, fields, remove_const(src_struct)))
00375         return true; /* Empty message type */
00376     
00377     do {
00378         if (PB_LTYPE(iter.pos->type) == PB_LTYPE_EXTENSION)
00379         {
00380             /* Special case for the extension field placeholder */
00381             if (!encode_extension_field(stream, iter.pos, iter.pData))
00382                 return false;
00383         }
00384         else
00385         {
00386             /* Regular field */
00387             if (!encode_field(stream, iter.pos, iter.pData))
00388                 return false;
00389         }
00390     } while (pb_field_iter_next(&iter));
00391     
00392     return true;
00393 }
00394 
00395 bool pb_encode_delimited(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
00396 {
00397     return pb_encode_submessage(stream, fields, src_struct);
00398 }
00399 
00400 bool pb_get_encoded_size(size_t *size, const pb_field_t fields[], const void *src_struct)
00401 {
00402     pb_ostream_t stream = PB_OSTREAM_SIZING;
00403     
00404     if (!pb_encode(&stream, fields, src_struct))
00405         return false;
00406     
00407     *size = stream.bytes_written;
00408     return true;
00409 }
00410 
00411 /********************
00412  * Helper functions *
00413  ********************/
00414 bool checkreturn pb_encode_varint(pb_ostream_t *stream, uint64_t value)
00415 {
00416     pb_byte_t buffer[10];
00417     size_t i = 0;
00418     
00419     if (value <= 0x7F)
00420     {
00421         pb_byte_t v = (pb_byte_t)value;
00422         return pb_write(stream, &v, 1);
00423     }
00424     
00425     while (value)
00426     {
00427         buffer[i] = (pb_byte_t)((value & 0x7F) | 0x80);
00428         value >>= 7;
00429         i++;
00430     }
00431     buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
00432     
00433     return pb_write(stream, buffer, i);
00434 }
00435 
00436 bool checkreturn pb_encode_svarint(pb_ostream_t *stream, int64_t value)
00437 {
00438     uint64_t zigzagged;
00439     if (value < 0)
00440         zigzagged = ~((uint64_t)value << 1);
00441     else
00442         zigzagged = (uint64_t)value << 1;
00443     
00444     return pb_encode_varint(stream, zigzagged);
00445 }
00446 
00447 bool checkreturn pb_encode_fixed32(pb_ostream_t *stream, const void *value)
00448 {
00449     uint32_t val = *(const uint32_t*)value;
00450     pb_byte_t bytes[4];
00451     bytes[0] = (pb_byte_t)(val & 0xFF);
00452     bytes[1] = (pb_byte_t)((val >> 8) & 0xFF);
00453     bytes[2] = (pb_byte_t)((val >> 16) & 0xFF);
00454     bytes[3] = (pb_byte_t)((val >> 24) & 0xFF);
00455     return pb_write(stream, bytes, 4);
00456 }
00457 
00458 bool checkreturn pb_encode_fixed64(pb_ostream_t *stream, const void *value)
00459 {
00460     uint64_t val = *(const uint64_t*)value;
00461     pb_byte_t bytes[8];
00462     bytes[0] = (pb_byte_t)(val & 0xFF);
00463     bytes[1] = (pb_byte_t)((val >> 8) & 0xFF);
00464     bytes[2] = (pb_byte_t)((val >> 16) & 0xFF);
00465     bytes[3] = (pb_byte_t)((val >> 24) & 0xFF);
00466     bytes[4] = (pb_byte_t)((val >> 32) & 0xFF);
00467     bytes[5] = (pb_byte_t)((val >> 40) & 0xFF);
00468     bytes[6] = (pb_byte_t)((val >> 48) & 0xFF);
00469     bytes[7] = (pb_byte_t)((val >> 56) & 0xFF);
00470     return pb_write(stream, bytes, 8);
00471 }
00472 
00473 bool checkreturn pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number)
00474 {
00475     uint64_t tag = ((uint64_t)field_number << 3) | wiretype;
00476     return pb_encode_varint(stream, tag);
00477 }
00478 
00479 bool checkreturn pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
00480 {
00481     pb_wire_type_t wiretype;
00482     switch (PB_LTYPE(field->type))
00483     {
00484         case PB_LTYPE_VARINT:
00485         case PB_LTYPE_UVARINT:
00486         case PB_LTYPE_SVARINT:
00487             wiretype = PB_WT_VARINT;
00488             break;
00489         
00490         case PB_LTYPE_FIXED32:
00491             wiretype = PB_WT_32BIT;
00492             break;
00493         
00494         case PB_LTYPE_FIXED64:
00495             wiretype = PB_WT_64BIT;
00496             break;
00497         
00498         case PB_LTYPE_BYTES:
00499         case PB_LTYPE_STRING:
00500         case PB_LTYPE_SUBMESSAGE:
00501             wiretype = PB_WT_STRING;
00502             break;
00503         
00504         default:
00505             PB_RETURN_ERROR(stream, "invalid field type");
00506     }
00507     
00508     return pb_encode_tag(stream, wiretype, field->tag);
00509 }
00510 
00511 bool checkreturn pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size)
00512 {
00513     if (!pb_encode_varint(stream, (uint64_t)size))
00514         return false;
00515     
00516     return pb_write(stream, buffer, size);
00517 }
00518 
00519 bool checkreturn pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
00520 {
00521     /* First calculate the message size using a non-writing substream. */
00522     pb_ostream_t substream = PB_OSTREAM_SIZING;
00523     size_t size;
00524     bool status;
00525     
00526     if (!pb_encode(&substream, fields, src_struct))
00527     {
00528 #ifndef PB_NO_ERRMSG
00529         stream->errmsg = substream.errmsg;
00530 #endif
00531         return false;
00532     }
00533     
00534     size = substream.bytes_written;
00535     
00536     if (!pb_encode_varint(stream, (uint64_t)size))
00537         return false;
00538     
00539     if (stream->callback == NULL)
00540         return pb_write(stream, NULL, size); /* Just sizing */
00541     
00542     if (stream->bytes_written + size > stream->max_size)
00543         PB_RETURN_ERROR(stream, "stream full");
00544         
00545     /* Use a substream to verify that a callback doesn't write more than
00546      * what it did the first time. */
00547     substream.callback = stream->callback;
00548     substream.state = stream->state;
00549     substream.max_size = size;
00550     substream.bytes_written = 0;
00551 #ifndef PB_NO_ERRMSG
00552     substream.errmsg = NULL;
00553 #endif
00554     
00555     status = pb_encode(&substream, fields, src_struct);
00556     
00557     stream->bytes_written += substream.bytes_written;
00558     stream->state = substream.state;
00559 #ifndef PB_NO_ERRMSG
00560     stream->errmsg = substream.errmsg;
00561 #endif
00562     
00563     if (substream.bytes_written != size)
00564         PB_RETURN_ERROR(stream, "submsg size changed");
00565     
00566     return status;
00567 }
00568 
00569 /* Field encoders */
00570 
00571 static bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00572 {
00573     int64_t value = 0;
00574     
00575     if (field->data_size == sizeof(int_least8_t))
00576         value = *(const int_least8_t*)src;
00577     else if (field->data_size == sizeof(int_least16_t))
00578         value = *(const int_least16_t*)src;
00579     else if (field->data_size == sizeof(int32_t))
00580         value = *(const int32_t*)src;
00581     else if (field->data_size == sizeof(int64_t))
00582         value = *(const int64_t*)src;
00583     else
00584         PB_RETURN_ERROR(stream, "invalid data_size");
00585     
00586     return pb_encode_varint(stream, (uint64_t)value);
00587 }
00588 
00589 static bool checkreturn pb_enc_uvarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00590 {
00591     uint64_t value = 0;
00592     
00593     if (field->data_size == sizeof(uint_least8_t))
00594         value = *(const uint_least8_t*)src;
00595     else if (field->data_size == sizeof(uint_least16_t))
00596         value = *(const uint_least16_t*)src;
00597     else if (field->data_size == sizeof(uint32_t))
00598         value = *(const uint32_t*)src;
00599     else if (field->data_size == sizeof(uint64_t))
00600         value = *(const uint64_t*)src;
00601     else
00602         PB_RETURN_ERROR(stream, "invalid data_size");
00603     
00604     return pb_encode_varint(stream, value);
00605 }
00606 
00607 static bool checkreturn pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00608 {
00609     int64_t value = 0;
00610     
00611     if (field->data_size == sizeof(int_least8_t))
00612         value = *(const int_least8_t*)src;
00613     else if (field->data_size == sizeof(int_least16_t))
00614         value = *(const int_least16_t*)src;
00615     else if (field->data_size == sizeof(int32_t))
00616         value = *(const int32_t*)src;
00617     else if (field->data_size == sizeof(int64_t))
00618         value = *(const int64_t*)src;
00619     else
00620         PB_RETURN_ERROR(stream, "invalid data_size");
00621     
00622     return pb_encode_svarint(stream, value);
00623 }
00624 
00625 static bool checkreturn pb_enc_fixed64(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00626 {
00627     PB_UNUSED(field);
00628     return pb_encode_fixed64(stream, src);
00629 }
00630 
00631 static bool checkreturn pb_enc_fixed32(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00632 {
00633     PB_UNUSED(field);
00634     return pb_encode_fixed32(stream, src);
00635 }
00636 
00637 static bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00638 {
00639     const pb_bytes_array_t *bytes = (const pb_bytes_array_t*)src;
00640     
00641     if (src == NULL)
00642     {
00643         /* Threat null pointer as an empty bytes field */
00644         return pb_encode_string(stream, NULL, 0);
00645     }
00646     
00647     if (PB_ATYPE(field->type) == PB_ATYPE_STATIC &&
00648         PB_BYTES_ARRAY_T_ALLOCSIZE(bytes->size) > field->data_size)
00649     {
00650         PB_RETURN_ERROR(stream, "bytes size exceeded");
00651     }
00652     
00653     return pb_encode_string(stream, bytes->bytes, bytes->size);
00654 }
00655 
00656 static bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00657 {
00658     size_t size = 0;
00659     size_t max_size = field->data_size;
00660     const char *p = (const char*)src;
00661     
00662     if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
00663         max_size = (size_t)-1;
00664 
00665     if (src == NULL)
00666     {
00667         size = 0; /* Threat null pointer as an empty string */
00668     }
00669     else
00670     {
00671         /* strnlen() is not always available, so just use a loop */
00672         while (size < max_size && *p != '\0')
00673         {
00674             size++;
00675             p++;
00676         }
00677     }
00678 
00679     return pb_encode_string(stream, (const pb_byte_t*)src, size);
00680 }
00681 
00682 static bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
00683 {
00684     if (field->ptr == NULL)
00685         PB_RETURN_ERROR(stream, "invalid field descriptor");
00686     
00687     return pb_encode_submessage(stream, (const pb_field_t*)field->ptr, src);
00688 }