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Diffstat (limited to 'tensorflow/core/lib/strings/strcat.h')
| -rw-r--r-- | tensorflow/core/lib/strings/strcat.h | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/tensorflow/core/lib/strings/strcat.h b/tensorflow/core/lib/strings/strcat.h new file mode 100644 index 0000000000..763ad8368a --- /dev/null +++ b/tensorflow/core/lib/strings/strcat.h @@ -0,0 +1,229 @@ +// #status: RECOMMENDED +// #category: operations on strings +// #summary: Merges strings or numbers with no delimiter. +// +#ifndef TENSORFLOW_LIB_STRINGS_STRCAT_H_ +#define TENSORFLOW_LIB_STRINGS_STRCAT_H_ + +#include <string> + +#include "tensorflow/core/lib/core/stringpiece.h" +#include "tensorflow/core/lib/strings/numbers.h" +#include "tensorflow/core/platform/port.h" + +// The AlphaNum type was designed to be used as the parameter type for StrCat(). +// Any routine accepting either a string or a number may accept it. +// The basic idea is that by accepting a "const AlphaNum &" as an argument +// to your function, your callers will automagically convert bools, integers, +// and floating point values to strings for you. +// +// NOTE: Use of AlphaNum outside of the //strings package is unsupported except +// for the specific case of function parameters of type "AlphaNum" or "const +// AlphaNum &". In particular, instantiating AlphaNum directly as a stack +// variable is not supported. +// +// Conversion from 8-bit values is not accepted because if it were, then an +// attempt to pass ':' instead of ":" might result in a 58 ending up in your +// result. +// +// Bools convert to "0" or "1". +// +// Floating point values are converted to a string which, if passed to strtod(), +// would produce the exact same original double (except in case of NaN; all NaNs +// are considered the same value). We try to keep the string short but it's not +// guaranteed to be as short as possible. +// +// You can convert to Hexadecimal output rather than Decimal output using Hex. +// To do this, pass strings::Hex(my_int) as a parameter to StrCat. You may +// specify a minimum field width using a separate parameter, so the equivalent +// of Printf("%04x", my_int) is StrCat(Hex(my_int, strings::ZERO_PAD_4)) +// +// This class has implicit constructors. +namespace tensorflow { +namespace strings { + +enum PadSpec { + NO_PAD = 1, + ZERO_PAD_2, + ZERO_PAD_3, + ZERO_PAD_4, + ZERO_PAD_5, + ZERO_PAD_6, + ZERO_PAD_7, + ZERO_PAD_8, + ZERO_PAD_9, + ZERO_PAD_10, + ZERO_PAD_11, + ZERO_PAD_12, + ZERO_PAD_13, + ZERO_PAD_14, + ZERO_PAD_15, + ZERO_PAD_16, +}; + +struct Hex { + uint64 value; + enum PadSpec spec; + template <class Int> + explicit Hex(Int v, PadSpec s = NO_PAD) + : spec(s) { + // Prevent sign-extension by casting integers to + // their unsigned counterparts. + static_assert( + sizeof(v) == 1 || sizeof(v) == 2 || sizeof(v) == 4 || sizeof(v) == 8, + "Unknown integer type"); + value = sizeof(v) == 1 + ? static_cast<uint8>(v) + : sizeof(v) == 2 ? static_cast<uint16>(v) + : sizeof(v) == 4 ? static_cast<uint32>(v) + : static_cast<uint64>(v); + } +}; + +class AlphaNum { + public: + // No bool ctor -- bools convert to an integral type. + // A bool ctor would also convert incoming pointers (bletch). + + AlphaNum(int i32) // NOLINT(runtime/explicit) + : piece_(digits_, FastInt32ToBufferLeft(i32, digits_) - &digits_[0]) {} + AlphaNum(unsigned int u32) // NOLINT(runtime/explicit) + : piece_(digits_, FastUInt32ToBufferLeft(u32, digits_) - &digits_[0]) {} + AlphaNum(long x) // NOLINT(runtime/explicit) + : piece_(digits_, FastInt64ToBufferLeft(x, digits_) - &digits_[0]) {} + AlphaNum(unsigned long x) // NOLINT(runtime/explicit) + : piece_(digits_, FastUInt64ToBufferLeft(x, digits_) - &digits_[0]) {} + AlphaNum(long long int i64) // NOLINT(runtime/explicit) + : piece_(digits_, FastInt64ToBufferLeft(i64, digits_) - &digits_[0]) {} + AlphaNum(unsigned long long int u64) // NOLINT(runtime/explicit) + : piece_(digits_, FastUInt64ToBufferLeft(u64, digits_) - &digits_[0]) {} + + AlphaNum(float f) // NOLINT(runtime/explicit) + : piece_(digits_, strlen(FloatToBuffer(f, digits_))) {} + AlphaNum(double f) // NOLINT(runtime/explicit) + : piece_(digits_, strlen(DoubleToBuffer(f, digits_))) {} + + AlphaNum(Hex hex); // NOLINT(runtime/explicit) + + AlphaNum(const char *c_str) : piece_(c_str) {} // NOLINT(runtime/explicit) + AlphaNum(const StringPiece &pc) : piece_(pc) {} // NOLINT(runtime/explicit) + AlphaNum(const tensorflow::string &str) // NOLINT(runtime/explicit) + : piece_(str) {} + + StringPiece::size_type size() const { return piece_.size(); } + const char *data() const { return piece_.data(); } + StringPiece Piece() const { return piece_; } + + private: + StringPiece piece_; + char digits_[kFastToBufferSize]; + + // Use ":" not ':' + AlphaNum(char c); // NOLINT(runtime/explicit) + + TF_DISALLOW_COPY_AND_ASSIGN(AlphaNum); +}; + +extern AlphaNum gEmptyAlphaNum; + +using strings::AlphaNum; +using strings::gEmptyAlphaNum; + +// ---------------------------------------------------------------------- +// StrCat() +// This merges the given strings or numbers, with no delimiter. This +// is designed to be the fastest possible way to construct a string out +// of a mix of raw C strings, StringPieces, strings, bool values, +// and numeric values. +// +// Don't use this for user-visible strings. The localization process +// works poorly on strings built up out of fragments. +// +// For clarity and performance, don't use StrCat when appending to a +// string. In particular, avoid using any of these (anti-)patterns: +// str.append(StrCat(...)) +// str += StrCat(...) +// str = StrCat(str, ...) +// where the last is the worse, with the potential to change a loop +// from a linear time operation with O(1) dynamic allocations into a +// quadratic time operation with O(n) dynamic allocations. StrAppend +// is a better choice than any of the above, subject to the restriction +// of StrAppend(&str, a, b, c, ...) that none of the a, b, c, ... may +// be a reference into str. +// ---------------------------------------------------------------------- + +// For performance reasons, we have specializations for <= 4 args. +string StrCat(const AlphaNum &a) TF_MUST_USE_RESULT; +string StrCat(const AlphaNum &a, const AlphaNum &b) TF_MUST_USE_RESULT; +string StrCat(const AlphaNum &a, const AlphaNum &b, + const AlphaNum &c) TF_MUST_USE_RESULT; +string StrCat(const AlphaNum &a, const AlphaNum &b, const AlphaNum &c, + const AlphaNum &d) TF_MUST_USE_RESULT; + +// inline definitions must be duplicated due to TF_MUST_USE_RESULT +inline string StrCat(const AlphaNum &a) { return string(a.data(), a.size()); } + +namespace internal { + +// Do not call directly - this is not part of the public API. +string CatPieces(std::initializer_list<StringPiece> pieces); +void AppendPieces(string *dest, std::initializer_list<StringPiece> pieces); + +} // namespace internal + +// Support 5 or more arguments +template <typename... AV> +string StrCat(const AlphaNum &a, const AlphaNum &b, const AlphaNum &c, + const AlphaNum &d, const AlphaNum &e, + const AV &... args) TF_MUST_USE_RESULT; + +template <typename... AV> +inline string StrCat(const AlphaNum &a, const AlphaNum &b, const AlphaNum &c, + const AlphaNum &d, const AlphaNum &e, const AV &... args) { + return internal::CatPieces({a.Piece(), b.Piece(), c.Piece(), d.Piece(), + e.Piece(), + static_cast<const AlphaNum &>(args).Piece()...}); +} + +// ---------------------------------------------------------------------- +// StrAppend() +// Same as above, but adds the output to the given string. +// WARNING: For speed, StrAppend does not try to check each of its input +// arguments to be sure that they are not a subset of the string being +// appended to. That is, while this will work: +// +// string s = "foo"; +// s += s; +// +// This will not (necessarily) work: +// +// string s = "foo"; +// StrAppend(&s, s); +// +// Note: while StrCat supports appending up to 26 arguments, StrAppend +// is currently limited to 9. That's rarely an issue except when +// automatically transforming StrCat to StrAppend, and can easily be +// worked around as consecutive calls to StrAppend are quite efficient. +// ---------------------------------------------------------------------- + +void StrAppend(string *dest, const AlphaNum &a); +void StrAppend(string *dest, const AlphaNum &a, const AlphaNum &b); +void StrAppend(string *dest, const AlphaNum &a, const AlphaNum &b, + const AlphaNum &c); +void StrAppend(string *dest, const AlphaNum &a, const AlphaNum &b, + const AlphaNum &c, const AlphaNum &d); + +// Support 5 or more arguments +template <typename... AV> +inline void StrAppend(string *dest, const AlphaNum &a, const AlphaNum &b, + const AlphaNum &c, const AlphaNum &d, const AlphaNum &e, + const AV &... args) { + internal::AppendPieces(dest, + {a.Piece(), b.Piece(), c.Piece(), d.Piece(), e.Piece(), + static_cast<const AlphaNum &>(args).Piece()...}); +} + +} // namespace strings +} // namespace tensorflow + +#endif // TENSORFLOW_LIB_STRINGS_STRCAT_H_ |