path: root/src/upb_decoder.c

/*
 * upb - a minimalist implementation of protocol buffers.
 *
 * Copyright (c) 2008-2009 Joshua Haberman.  See LICENSE for details.
 */

#include "upb_decoder.h"

#include <inttypes.h>
#include <stddef.h>
#include <stdlib.h>
#include "upb_def.h"

/* Functions to read wire values. *********************************************/

// These functions are internal to the decode, but might be moved into an
// internal header file if we at some point in the future opt to do code
// generation, because the generated code would want to inline these functions.
// The same applies to the functions to read .proto values below.

const uint8_t *upb_get_v_uint64_t_full(const uint8_t *buf, const uint8_t *end,
                                       uint64_t *val, upb_status *status);

// Gets a varint (wire type: UPB_WIRE_TYPE_VARINT).
INLINE const uint8_t *upb_get_v_uint64_t(const uint8_t *buf, const uint8_t *end,
                                         uint64_t *val, upb_status *status)
{
  // We inline this common case (1-byte varints), if that fails we dispatch to
  // the full (non-inlined) version.
  if((*buf & 0x80) == 0) {
    *val = *buf & 0x7f;
    return buf + 1;
  } else {
    return upb_get_v_uint64_t_full(buf, end, val, status);
  }
}

// Gets a varint -- called when we only need 32 bits of it.  Note that a 32-bit
// varint is not a true wire type.
INLINE const uint8_t *upb_get_v_uint32_t(const uint8_t *buf, const uint8_t *end,
                                         uint32_t *val, upb_status *status)
{
  uint64_t val64;
  const uint8_t *ret = upb_get_v_uint64_t(buf, end, &val64, status);
  *val = (uint32_t)val64;  // Discard the high bits.
  return ret;
}

// Gets a fixed-length 32-bit integer (wire type: UPB_WIRE_TYPE_32BIT).
INLINE const uint8_t *upb_get_f_uint32_t(const uint8_t *buf, const uint8_t *end,
                                         uint32_t *val, upb_status *status)
{
  const uint8_t *uint32_end = buf + sizeof(uint32_t);
  if(uint32_end > end) {
    status->code = UPB_STATUS_NEED_MORE_DATA;
    return end;
  }
#if UPB_UNALIGNED_READS_OK
  *val = *(uint32_t*)buf;
#else
#define SHL(val, bits) ((uint32_t)val << bits)
  *val = SHL(buf[0], 0) | SHL(buf[1], 8) | SHL(buf[2], 16) | SHL(buf[3], 24);
#undef SHL
#endif
  return uint32_end;
}

// Gets a fixed-length 64-bit integer (wire type: UPB_WIRE_TYPE_64BIT).
INLINE const uint8_t *upb_get_f_uint64_t(const uint8_t *buf, const uint8_t *end,
                                         uint64_t *val, upb_status *status)
{
  const uint8_t *uint64_end = buf + sizeof(uint64_t);
  if(uint64_end > end) {
    status->code = UPB_STATUS_NEED_MORE_DATA;
    return end;
  }
#if UPB_UNALIGNED_READS_OK
  *val = *(uint64_t*)buf;
#else
#define SHL(val, bits) ((uint64_t)val << bits)
  *val = SHL(buf[0],  0) | SHL(buf[1],  8) | SHL(buf[2], 16) | SHL(buf[3], 24) |
         SHL(buf[4], 32) | SHL(buf[5], 40) | SHL(buf[6], 48) | SHL(buf[7], 56);
#undef SHL
#endif
  return uint64_end;
}

INLINE const uint8_t *upb_skip_v_uint64_t(const uint8_t *buf,
                                          const uint8_t *end,
                                          upb_status *status)
{
  const uint8_t *const maxend = buf + 10;
  uint8_t last = 0x80;
  for(; buf < (uint8_t*)end && (last & 0x80); buf++)
    last = *buf;

  if(buf >= end && buf <= maxend && (last & 0x80)) {
    status->code = UPB_STATUS_NEED_MORE_DATA;
    buf = end;
  } else if(buf > maxend) {
    status->code = UPB_ERROR_UNTERMINATED_VARINT;
    buf = end;
  }
  return buf;
}

INLINE const uint8_t *upb_skip_f_uint32_t(const uint8_t *buf,
                                          const uint8_t *end,
                                          upb_status *status)
{
  const uint8_t *uint32_end = buf + sizeof(uint32_t);
  if(uint32_end > end) {
    status->code = UPB_STATUS_NEED_MORE_DATA;
    return end;
  }
  return uint32_end;
}

INLINE const uint8_t *upb_skip_f_uint64_t(const uint8_t *buf,
                                          const uint8_t *end,
                                          upb_status *status)
{
  const uint8_t *uint64_end = buf + sizeof(uint64_t);
  if(uint64_end > end) {
    status->code = UPB_STATUS_NEED_MORE_DATA;
    return end;
  }
  return uint64_end;
}

/* Functions to read .proto values. *******************************************/

// Performs zig-zag decoding, which is used by sint32 and sint64.
INLINE int32_t upb_zzdec_32(uint32_t n) { return (n >> 1) ^ -(int32_t)(n & 1); }
INLINE int64_t upb_zzdec_64(uint64_t n) { return (n >> 1) ^ -(int64_t)(n & 1); }

// Use macros to define a set of two functions for each .proto type:
//
//  // Reads and converts a .proto value from buf, placing it in d.
//  // "end" indicates the end of the current buffer (if the buffer does
//  // not contain the entire value UPB_STATUS_NEED_MORE_DATA is returned).
//  // On success, a pointer will be returned to the first byte that was
//  // not consumed.
//  const uint8_t *upb_get_INT32(const uint8_t *buf, const uint8_t *end,
//                               int32_t *d, upb_status *status);
//
//  // Given an already read wire value s (source), convert it to a .proto
//  // value and return it.
//  int32_t upb_wvtov_INT32(uint32_t s);
//
// These are the most efficient functions to call if you want to decode a value
// for a known type.

#define WVTOV(type, wire_t, val_t) \
  INLINE val_t upb_wvtov_ ## type(wire_t s)

#define GET(type, v_or_f, wire_t, val_t, member_name) \
  INLINE const uint8_t *upb_get_ ## type(const uint8_t *buf, const uint8_t *end, \
                                         val_t *d, upb_status *status) { \
    wire_t tmp = 0; \
    const uint8_t *ret = upb_get_ ## v_or_f ## _ ## wire_t(buf, end, &tmp, status); \
    *d = upb_wvtov_ ## type(tmp); \
    return ret; \
  }

#define T(type, v_or_f, wire_t, val_t, member_name) \
  WVTOV(type, wire_t, val_t);  /* prototype for GET below */ \
  GET(type, v_or_f, wire_t, val_t, member_name) \
  WVTOV(type, wire_t, val_t)

T(INT32,    v, uint32_t, int32_t,  int32)   { return (int32_t)s;      }
T(INT64,    v, uint64_t, int64_t,  int64)   { return (int64_t)s;      }
T(UINT32,   v, uint32_t, uint32_t, uint32)  { return s;               }
T(UINT64,   v, uint64_t, uint64_t, uint64)  { return s;               }
T(SINT32,   v, uint32_t, int32_t,  int32)   { return upb_zzdec_32(s); }
T(SINT64,   v, uint64_t, int64_t,  int64)   { return upb_zzdec_64(s); }
T(FIXED32,  f, uint32_t, uint32_t, uint32)  { return s;               }
T(FIXED64,  f, uint64_t, uint64_t, uint64)  { return s;               }
T(SFIXED32, f, uint32_t, int32_t,  int32)   { return (int32_t)s;      }
T(SFIXED64, f, uint64_t, int64_t,  int64)   { return (int64_t)s;      }
T(BOOL,     v, uint32_t, bool,     _bool)   { return (bool)s;         }
T(ENUM,     v, uint32_t, int32_t,  int32)   { return (int32_t)s;      }
T(DOUBLE,   f, uint64_t, double,   _double) {
  upb_value v;
  v.uint64 = s;
  return v._double;
}
T(FLOAT,    f, uint32_t, float,    _float)  {
  upb_value v;
  v.uint32 = s;
  return v._float;
}

#undef WVTOV
#undef GET
#undef T

// Parses a 64-bit varint that is known to be >= 2 bytes (the inline version
// handles 1 and 2 byte varints).
const uint8_t *upb_get_v_uint64_t_full(const uint8_t *buf, const uint8_t *end,
                                       uint64_t *val, upb_status *status)
{
  const uint8_t *const maxend = buf + 10;
  uint8_t last = 0x80;
  *val = 0;
  int bitpos;

  for(bitpos = 0; buf < (uint8_t*)end && (last & 0x80); buf++, bitpos += 7)
    *val |= ((uint64_t)((last = *buf) & 0x7F)) << bitpos;

  if(buf >= end && buf <= maxend && (last & 0x80)) {
    upb_seterr(status, UPB_STATUS_NEED_MORE_DATA,
               "Provided data ended in the middle of a varint.\n");
    buf = end;
  } else if(buf > maxend) {
    upb_seterr(status, UPB_ERROR_UNTERMINATED_VARINT,
               "Varint was unterminated after 10 bytes.\n");
    buf = end;
  }

  return buf;
}

// Advances buf past the current wire value (of type wt), saving the result in
// outbuf.
static const uint8_t *skip_wire_value(const uint8_t *buf, const uint8_t *end,
                                      upb_wire_type_t wt, upb_status *status)
{
  switch(wt) {
    case UPB_WIRE_TYPE_VARINT:
      return upb_skip_v_uint64_t(buf, end, status);
    case UPB_WIRE_TYPE_64BIT:
      return upb_skip_f_uint64_t(buf, end, status);
    case UPB_WIRE_TYPE_32BIT:
      return upb_skip_f_uint32_t(buf, end, status);
    case UPB_WIRE_TYPE_START_GROUP:
      // TODO: skip to matching end group.
    case UPB_WIRE_TYPE_END_GROUP:
      return buf;
    default:
      status->code = UPB_STATUS_ERROR;
      return end;
  }
}

static const uint8_t *upb_decode_value(const uint8_t *buf, const uint8_t *end,
                                       upb_field_type_t ft, upb_valueptr v,
                                       upb_status *status)
{
#define CASE(t, member_name) \
  case UPB_TYPE(t): return upb_get_ ## t(buf, end, v.member_name, status);

  switch(ft) {
    CASE(DOUBLE,   _double)
    CASE(FLOAT,    _float)
    CASE(INT32,    int32)
    CASE(INT64,    int64)
    CASE(UINT32,   uint32)
    CASE(UINT64,   uint64)
    CASE(SINT32,   int32)
    CASE(SINT64,   int64)
    CASE(FIXED32,  uint32)
    CASE(FIXED64,  uint64)
    CASE(SFIXED32, int32)
    CASE(SFIXED64, int64)
    CASE(BOOL,     _bool)
    CASE(ENUM,     int32)
    default: return end;
  }

#undef CASE
}

// The decoder keeps a stack with one entry per level of recursion.
// upb_decoder_frame is one frame of that stack.
typedef struct {
  upb_msgdef *msgdef;
  upb_fielddef *field;
  int32_t end_offset;  // For groups, 0.
} upb_decoder_frame;

struct upb_decoder {
  // Immutable state of the decoder.
  upb_msgdef *toplevel_msgdef;
  upb_bytesrc *bytesrc;

  // State pertaining to a particular decode (resettable).
  // Stack entries store the offset where the submsg ends (for groups, 0).
  upb_decoder_frame stack[UPB_MAX_NESTING], *top, *limit;

  // The current buffer.
  upb_string *buf;

  // The overall stream offset of the beginning of this buffer.
  uint32_t stream_offset;

  // The current offset in this buffer.
  uint32_t buffer_offset;
};

upb_decoder *upb_decoder_new(upb_msgdef *msgdef)
{
  upb_decoder *d = malloc(sizeof(*d));
  d->toplevel_msgdef = msgdef;
  d->limit = &d->stack[UPB_MAX_NESTING];
  return d;
}

void upb_decoder_free(upb_decoder *d)
{
  free(d);
}

void upb_decoder_reset(upb_decoder *d, upb_sink *sink)
{
  d->top = d->stack;
  d->completed_offset = 0;
  d->sink = sink;
  d->top->msgdef = d->toplevel_msgdef;
  // The top-level message is not delimited (we can keep receiving data for it
  // indefinitely), so we treat it like a group.
  d->top->end_offset = 0;
}



static const void *get_msgend(upb_decoder *d, const uint8_t *start)
{
  if(d->top->end_offset > 0)
    return start + (d->top->end_offset - d->completed_offset);
  else
    return (void*)UINTPTR_MAX;  // group.
}

static bool isgroup(const void *submsg_end)
{
  return submsg_end == (void*)UINTPTR_MAX;
}

extern upb_wire_type_t upb_expected_wire_types[];
// Returns true if wt is the correct on-the-wire type for ft.
INLINE bool upb_check_type(upb_wire_type_t wt, upb_field_type_t ft) {
  // This doesn't currently support packed arrays.
  return upb_types[ft].expected_wire_type == wt;
}


// Pushes a new stack frame for a submessage with the given len (which will
// be zero if the submessage is a group).
static const uint8_t *push(upb_decoder *d, const uint8_t *start,
                           uint32_t submsg_len, upb_fielddef *f,
                           upb_status *status)
{
  d->top->field = f;
  d->top++;
  if(d->top >= d->limit) {
    upb_seterr(status, UPB_ERROR_MAX_NESTING_EXCEEDED,
               "Nesting exceeded maximum (%d levels)\n",
               UPB_MAX_NESTING);
    return NULL;
  }
  upb_decoder_frame *frame = d->top;
  frame->end_offset = d->completed_offset + submsg_len;
  frame->msgdef = upb_downcast_msgdef(f->def);

  upb_sink_onstart(d->sink, f, status);
  return get_msgend(d, start);
}

// Pops a stack frame, returning a pointer for where the next submsg should
// end (or a pointer that is out of range for a group).
static const void *pop(upb_decoder *d, const uint8_t *start, upb_status *status)
{
  d->top--;
  upb_sink_onend(d->sink, d->top->field, status);
  return get_msgend(d, start);
}

// Parses a tag, places the result in *tag.
upb_fielddef *upb_decoder_src_getdef(upb_decoder *d)
{
  uint32_t key;
  upb_fill_buffer(d);
  d->buf = upb_get_v_uint32_t(d->buf, d->end, &key, &d->status);
  if (!upb_ok(status)) return NULL;
  if(upb_wiretype_from_key(key) == UPB_WIRE_TYPE_END_GROUP) {
    if(!isgroup(d->submsg_end)) {
      upb_seterr(d->status, UPB_STATUS_ERROR, "End group seen but current "
                 "message is not a group, byte offset: %zd",
                 d->completed_offset + (completed - start));
      return NULL;
    }
    submsg_end = pop(d, start, status);
    msgdef = d->top->msgdef;
    completed = buf;
    return NULL;
  }
  // Look up field by tag number.
  return upb_msg_itof(d->top->msgdef, upb_fieldnum_from_key(key));
}

bool upb_decoder_src_getval(upb_src *src, upb_valueptr val)
{
  if(upb_wiretype_from_key(d->key) == UPB_WIRE_TYPE_DELIMITED) {
    int32_t delim_len;
    d->buf = upb_get_INT32(d->buf, d->end, &delim_len, &d->status);
    CHECK_STATUS();  // Checking decode_tag() and upb_get_INT32().
    int32_t needed = 
    const uint8_t *delim_end = buf + delim_len;
    if(f->type == UPB_TYPE(MESSAGE)) {
      submsg_end = push(d, start, delim_end - start, f, status);
      msgdef = d->top->msgdef;
    } else {
      if(f && upb_isstringtype(f->type)) {
        int32_t str_start = buf - start;
        uint32_t len = str_start + delim_len;
        sink_status = upb_sink_onstr(d->sink, f, str, str_start, len, status);
      } // else { TODO: packed arrays }
      // If field was not found, it is skipped silently.
      buf = delim_end;  // Could be >end.
    }
  } else {
    if(!upb_check_type(tag.wire_type, f->type)) {
      buf = skip_wire_value(buf, end, tag.wire_type, status);
    } else if (f->type == UPB_TYPE(GROUP)) {
      submsg_end = push(d, start, 0, f, status);
      msgdef = d->top->msgdef;
    } else {
      upb_value val;
      buf = upb_decode_value(buf, end, f->type, upb_value_addrof(&val),
                            status);
      CHECK_STATUS();  // Checking upb_decode_value().
      sink_status = upb_sink_onvalue(d->sink, f, val, status);
    }
  }
  CHECK_STATUS();

  while(buf >= submsg_end) {
    if(buf > submsg_end) {
      upb_seterr(status, UPB_STATUS_ERROR, "Expected submsg end offset "
                 "did not lie on a tag/value boundary.");
      goto err;
    }
    submsg_end = pop(d, start, status);
    msgdef = d->top->msgdef;
  }
  // while(buf < d->packed_end) { TODO: packed arrays }
  completed = buf;
}

  // buf is our current offset, moves from start to end.
  const uint8_t *buf = (uint8_t*)upb_string_getrobuf(str);
  const uint8_t *const start = buf;  // ptr equivalent of d->completed_offset
  const uint8_t *const end = buf + upb_strlen(str);

  // When we have fully decoded a tag/value pair, we advance this.
  const uint8_t *completed = buf;

  const uint8_t *submsg_end = get_msgend(d, start);
  upb_msgdef *msgdef = d->top->msgdef;
  upb_sink_status sink_status = UPB_SINK_CONTINUE;

  // We need to check the status of operations that can fail, but we do so as
  // late as possible to avoid introducing branches that have to wait on
  // (status->code) which must be loaded from memory.  We must always check
  // before calling a user callback.
#define CHECK_STATUS() do { if(!upb_ok(status)) goto err; } while(0)

  // Main loop: executed once per tag/field pair.
  while(sink_status == UPB_SINK_CONTINUE && buf < end) {
    // Parse/handle tag.
    upb_tag tag;
    buf = decode_tag(buf, end, &tag, status);
    // Parse/handle field.
  }

  size_t read;
err:
  read = (char*)completed - (char*)start;
  d->completed_offset += read;
  return read;
}