chromium/components/cbor/reader.h

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_CBOR_READER_H_
#define COMPONENTS_CBOR_READER_H_

#include <stddef.h>

#include <map>
#include <optional>

#include "base/containers/span.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_span.h"
#include "components/cbor/cbor_export.h"
#include "components/cbor/values.h"

// Concise Binary Object Representation (CBOR) decoder as defined by
// https://tools.ietf.org/html/rfc7049. This decoder only accepts canonical CBOR
// as defined by section 3.9.
//
// This implementation supports the following major types:
//  - 0: Unsigned integers, up to 64-bit values*.
//  - 1: Signed integers, up to 64-bit values*.
//  - 2: Byte strings.
//  - 3: UTF-8 strings.
//  - 4: Definite-length arrays.
//  - 5: Definite-length maps.
//  - 7: Simple values or floating point values.
//
//  * Note: For simplicity, this implementation represents both signed and
//    unsigned integers with signed int64_t. This reduces the effective range
//    of unsigned integers.
//
// Requirements for canonical CBOR representation:
//  - Duplicate keys in maps are not allowed.
//  - Keys for maps must be sorted first by length and then by byte-wise
//    lexical order, as defined in Section 3.9.
//
// Known limitations and interpretations of the RFC (and the reasons):
//  - Does not support indefinite-length data streams or semantic tags (major
//    type 6). (Simplicity; security)
//  - Does not support the floating point and BREAK stop code value types in
//    major type 7. (Simplicity)
//  - Does not support non-character codepoints in major type 3. (Security)
//  - Treats incomplete CBOR data items as syntax errors. (Security)
//  - Treats trailing data bytes as errors. (Security)
//  - Treats unknown additional information formats as syntax errors.
//    (Simplicity; security)
//  - Limits CBOR value inputs to at most 16 layers of nesting. Callers can
//    enforce more shallow nesting by setting |max_nesting_level|. (Efficiency;
//    security)
//  - Only supports CBOR maps with integer or string type keys, due to the
//    cost of serialization when sorting map keys. (Efficiency; simplicity)
//  - Does not support simple values that are unassigned/reserved as per RFC
//    7049, and treats them as errors. (Security)

namespace cbor {

class CBOR_EXPORT Reader { … };

}  // namespace cbor

#endif  // COMPONENTS_CBOR_READER_H_