varint.h

/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
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 * modification, are permitted provided that the following conditions are
 * met:
 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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#ifndef GRPC_INTERNAL_CORE_TRANSPORT_CHTTP2_VARINT_H
#define GRPC_INTERNAL_CORE_TRANSPORT_CHTTP2_VARINT_H

#include <grpc/support/port_platform.h>

/* Helpers for hpack varint encoding */

/* length of a value that needs varint tail encoding (it's bigger than can be
   bitpacked into the opcode byte) - returned value includes the length of the
   opcode byte */
int grpc_chttp2_hpack_varint_length(gpr_uint32 tail_value);

void grpc_chttp2_hpack_write_varint_tail(gpr_uint32 tail_value,
                                         gpr_uint8* target, int tail_length);

/* maximum value that can be bitpacked with the opcode if the opcode has a
   prefix
   of length prefix_bits */
#define GRPC_CHTTP2_MAX_IN_PREFIX(prefix_bits) ((1 << (8 - (prefix_bits))) - 1)

/* length required to bitpack a value */
#define GRPC_CHTTP2_VARINT_LENGTH(n, prefix_bits) \
  ((n) < GRPC_CHTTP2_MAX_IN_PREFIX(prefix_bits)   \
       ? 1                                        \
       : grpc_chttp2_hpack_varint_length(         \
             (n) - GRPC_CHTTP2_MAX_IN_PREFIX(prefix_bits)))

#define GRPC_CHTTP2_WRITE_VARINT(n, prefix_bits, prefix_or, target, length) \
  do {                                                                      \
    gpr_uint8* tgt = target;                                                \
    if ((length) == 1) {                                                    \
      (tgt)[0] = (prefix_or) | (n);                                         \
    } else {                                                                \
      (tgt)[0] = (prefix_or) | GRPC_CHTTP2_MAX_IN_PREFIX(prefix_bits);      \
      grpc_chttp2_hpack_write_varint_tail(                                  \
          (n) - GRPC_CHTTP2_MAX_IN_PREFIX(prefix_bits), (tgt) + 1,          \
          (length) - 1);                                                    \
    }                                                                       \
  } while (0)

#endif  /* GRPC_INTERNAL_CORE_TRANSPORT_CHTTP2_VARINT_H */