SPIRV-Tools/source/util/parse_number.h
dan sinclair eda2cfbe12
Cleanup includes. (#1795)
This Cl cleans up the include paths to be relative to the top level
directory. Various include-what-you-use fixes have been added.
2018-08-03 15:06:09 -04:00

253 lines
9.6 KiB
C++

// Copyright (c) 2016 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef SOURCE_UTIL_PARSE_NUMBER_H_
#define SOURCE_UTIL_PARSE_NUMBER_H_
#include <functional>
#include <string>
#include <tuple>
#include "source/util/hex_float.h"
#include "spirv-tools/libspirv.h"
namespace spvtools {
namespace utils {
// A struct to hold the expected type information for the number in text to be
// parsed.
struct NumberType {
uint32_t bitwidth;
// SPV_NUMBER_NONE means the type is unknown and is invalid to be used with
// ParseAndEncode{|Integer|Floating}Number().
spv_number_kind_t kind;
};
// Returns true if the type is a scalar integer type.
inline bool IsIntegral(const NumberType& type) {
return type.kind == SPV_NUMBER_UNSIGNED_INT ||
type.kind == SPV_NUMBER_SIGNED_INT;
}
// Returns true if the type is a scalar floating point type.
inline bool IsFloating(const NumberType& type) {
return type.kind == SPV_NUMBER_FLOATING;
}
// Returns true if the type is a signed value.
inline bool IsSigned(const NumberType& type) {
return type.kind == SPV_NUMBER_FLOATING || type.kind == SPV_NUMBER_SIGNED_INT;
}
// Returns true if the type is unknown.
inline bool IsUnknown(const NumberType& type) {
return type.kind == SPV_NUMBER_NONE;
}
// Returns the number of bits in the type. This is only valid for integer and
// floating types.
inline int AssumedBitWidth(const NumberType& type) {
switch (type.kind) {
case SPV_NUMBER_SIGNED_INT:
case SPV_NUMBER_UNSIGNED_INT:
case SPV_NUMBER_FLOATING:
return type.bitwidth;
default:
break;
}
// We don't care about this case.
return 0;
}
// A templated class with a static member function Clamp, where Clamp sets a
// referenced value of type T to 0 if T is an unsigned integer type, and
// returns true if it modified the referenced value.
template <typename T, typename = void>
class ClampToZeroIfUnsignedType {
public:
// The default specialization does not clamp the value.
static bool Clamp(T*) { return false; }
};
// The specialization of ClampToZeroIfUnsignedType for unsigned integer types.
template <typename T>
class ClampToZeroIfUnsignedType<
T, typename std::enable_if<std::is_unsigned<T>::value>::type> {
public:
static bool Clamp(T* value_pointer) {
if (*value_pointer) {
*value_pointer = 0;
return true;
}
return false;
}
};
// Returns true if the given value fits within the target scalar integral type.
// The target type may have an unusual bit width. If the value was originally
// specified as a hexadecimal number, then the overflow bits should be zero.
// If it was hex and the target type is signed, then return the sign-extended
// value through the updated_value_for_hex pointer argument. On failure,
// returns false.
template <typename T>
bool CheckRangeAndIfHexThenSignExtend(T value, const NumberType& type,
bool is_hex, T* updated_value_for_hex) {
// The encoded result has three regions of bits that are of interest, from
// least to most significant:
// - magnitude bits, where the magnitude of the number would be stored if
// we were using a signed-magnitude representation.
// - an optional sign bit
// - overflow bits, up to bit 63 of a 64-bit number
// For example:
// Type Overflow Sign Magnitude
// --------------- -------- ---- ---------
// unsigned 8 bit 8-63 n/a 0-7
// signed 8 bit 8-63 7 0-6
// unsigned 16 bit 16-63 n/a 0-15
// signed 16 bit 16-63 15 0-14
// We'll use masks to define the three regions.
// At first we'll assume the number is unsigned.
const uint32_t bit_width = AssumedBitWidth(type);
uint64_t magnitude_mask =
(bit_width == 64) ? -1 : ((uint64_t(1) << bit_width) - 1);
uint64_t sign_mask = 0;
uint64_t overflow_mask = ~magnitude_mask;
if (value < 0 || IsSigned(type)) {
// Accommodate the sign bit.
magnitude_mask >>= 1;
sign_mask = magnitude_mask + 1;
}
bool failed = false;
if (value < 0) {
// The top bits must all be 1 for a negative signed value.
failed = ((value & overflow_mask) != overflow_mask) ||
((value & sign_mask) != sign_mask);
} else {
if (is_hex) {
// Hex values are a bit special. They decode as unsigned values, but may
// represent a negative number. In this case, the overflow bits should
// be zero.
failed = (value & overflow_mask) != 0;
} else {
const uint64_t value_as_u64 = static_cast<uint64_t>(value);
// Check overflow in the ordinary case.
failed = (value_as_u64 & magnitude_mask) != value_as_u64;
}
}
if (failed) {
return false;
}
// Sign extend hex the number.
if (is_hex && (value & sign_mask))
*updated_value_for_hex = (value | overflow_mask);
return true;
}
// Parses a numeric value of a given type from the given text. The number
// should take up the entire string, and should be within bounds for the target
// type. On success, returns true and populates the object referenced by
// value_pointer. On failure, returns false.
template <typename T>
bool ParseNumber(const char* text, T* value_pointer) {
// C++11 doesn't define std::istringstream(int8_t&), so calling this method
// with a single-byte type leads to implementation-defined behaviour.
// Similarly for uint8_t.
static_assert(sizeof(T) > 1,
"Single-byte types are not supported in this parse method");
if (!text) return false;
std::istringstream text_stream(text);
// Allow both decimal and hex input for integers.
// It also allows octal input, but we don't care about that case.
text_stream >> std::setbase(0);
text_stream >> *value_pointer;
// We should have read something.
bool ok = (text[0] != 0) && !text_stream.bad();
// It should have been all the text.
ok = ok && text_stream.eof();
// It should have been in range.
ok = ok && !text_stream.fail();
// Work around a bug in the GNU C++11 library. It will happily parse
// "-1" for uint16_t as 65535.
if (ok && text[0] == '-')
ok = !ClampToZeroIfUnsignedType<T>::Clamp(value_pointer);
return ok;
}
// Enum to indicate the parsing and encoding status.
enum class EncodeNumberStatus {
kSuccess = 0,
// Unsupported bit width etc.
kUnsupported,
// Expected type (NumberType) is not a scalar int or float, or putting a
// negative number in an unsigned literal.
kInvalidUsage,
// Number value does not fit the bit width of the expected type etc.
kInvalidText,
};
// Parses an integer value of a given |type| from the given |text| and encodes
// the number by the given |emit| function. On success, returns
// EncodeNumberStatus::kSuccess and the parsed number will be consumed by the
// given |emit| function word by word (least significant word first). On
// failure, this function returns the error code of the encoding status and
// |emit| function will not be called. If the string pointer |error_msg| is not
// a nullptr, it will be overwritten with error messages in case of failure. In
// case of success, |error_msg| will not be touched. Integers up to 64 bits are
// supported.
EncodeNumberStatus ParseAndEncodeIntegerNumber(
const char* text, const NumberType& type,
std::function<void(uint32_t)> emit, std::string* error_msg);
// Parses a floating point value of a given |type| from the given |text| and
// encodes the number by the given |emit| funciton. On success, returns
// EncodeNumberStatus::kSuccess and the parsed number will be consumed by the
// given |emit| function word by word (least significant word first). On
// failure, this function returns the error code of the encoding status and
// |emit| function will not be called. If the string pointer |error_msg| is not
// a nullptr, it will be overwritten with error messages in case of failure. In
// case of success, |error_msg| will not be touched. Only 16, 32 and 64 bit
// floating point numbers are supported.
EncodeNumberStatus ParseAndEncodeFloatingPointNumber(
const char* text, const NumberType& type,
std::function<void(uint32_t)> emit, std::string* error_msg);
// Parses an integer or floating point number of a given |type| from the given
// |text| and encodes the number by the given |emit| function. On success,
// returns EncodeNumberStatus::kSuccess and the parsed number will be consumed
// by the given |emit| function word by word (least significant word first). On
// failure, this function returns the error code of the encoding status and
// |emit| function will not be called. If the string pointer |error_msg| is not
// a nullptr, it will be overwritten with error messages in case of failure. In
// case of success, |error_msg| will not be touched. Integers up to 64 bits
// and 16/32/64 bit floating point values are supported.
EncodeNumberStatus ParseAndEncodeNumber(const char* text,
const NumberType& type,
std::function<void(uint32_t)> emit,
std::string* error_msg);
} // namespace utils
} // namespace spvtools
#endif // SOURCE_UTIL_PARSE_NUMBER_H_