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| -rw-r--r-- | intl/icu/source/common/unicode/bytestream.h | 307 |
1 files changed, 307 insertions, 0 deletions
diff --git a/intl/icu/source/common/unicode/bytestream.h b/intl/icu/source/common/unicode/bytestream.h new file mode 100644 index 0000000000..997746e428 --- /dev/null +++ b/intl/icu/source/common/unicode/bytestream.h @@ -0,0 +1,307 @@ +// © 2016 and later: Unicode, Inc. and others. +// License & terms of use: http://www.unicode.org/copyright.html +// Copyright (C) 2009-2012, International Business Machines +// Corporation and others. All Rights Reserved. +// +// Copyright 2007 Google Inc. All Rights Reserved. +// Author: sanjay@google.com (Sanjay Ghemawat) +// +// Abstract interface that consumes a sequence of bytes (ByteSink). +// +// Used so that we can write a single piece of code that can operate +// on a variety of output string types. +// +// Various implementations of this interface are provided: +// ByteSink: +// CheckedArrayByteSink Write to a flat array, with bounds checking +// StringByteSink Write to an STL string + +// This code is a contribution of Google code, and the style used here is +// a compromise between the original Google code and the ICU coding guidelines. +// For example, data types are ICU-ified (size_t,int->int32_t), +// and API comments doxygen-ified, but function names and behavior are +// as in the original, if possible. +// Assertion-style error handling, not available in ICU, was changed to +// parameter "pinning" similar to UnicodeString. +// +// In addition, this is only a partial port of the original Google code, +// limited to what was needed so far. The (nearly) complete original code +// is in the ICU svn repository at icuhtml/trunk/design/strings/contrib +// (see ICU ticket 6765, r25517). + +#ifndef __BYTESTREAM_H__ +#define __BYTESTREAM_H__ + +/** + * \file + * \brief C++ API: Interface for writing bytes, and implementation classes. + */ + +#include "unicode/utypes.h" + +#if U_SHOW_CPLUSPLUS_API + +#include "unicode/uobject.h" +#include "unicode/std_string.h" + +U_NAMESPACE_BEGIN + +/** + * A ByteSink can be filled with bytes. + * @stable ICU 4.2 + */ +class U_COMMON_API ByteSink : public UMemory { +public: + /** + * Default constructor. + * @stable ICU 4.2 + */ + ByteSink() { } + /** + * Virtual destructor. + * @stable ICU 4.2 + */ + virtual ~ByteSink(); + + /** + * Append "bytes[0,n-1]" to this. + * @param bytes the pointer to the bytes + * @param n the number of bytes; must be non-negative + * @stable ICU 4.2 + */ + virtual void Append(const char* bytes, int32_t n) = 0; + + /** + * Appends n bytes to this. Same as Append(). + * Call AppendU8() with u8"string literals" which are const char * in C++11 + * but const char8_t * in C++20. + * If the compiler does support char8_t as a distinct type, + * then an AppendU8() overload for that is defined and will be chosen. + * + * @param bytes the pointer to the bytes + * @param n the number of bytes; must be non-negative + * @stable ICU 67 + */ + inline void AppendU8(const char* bytes, int32_t n) { + Append(bytes, n); + } + +#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN) + /** + * Appends n bytes to this. Same as Append() but for a const char8_t * pointer. + * Call AppendU8() with u8"string literals" which are const char * in C++11 + * but const char8_t * in C++20. + * If the compiler does support char8_t as a distinct type, + * then this AppendU8() overload for that is defined and will be chosen. + * + * @param bytes the pointer to the bytes + * @param n the number of bytes; must be non-negative + * @stable ICU 67 + */ + inline void AppendU8(const char8_t* bytes, int32_t n) { + Append(reinterpret_cast<const char*>(bytes), n); + } +#endif + + /** + * Returns a writable buffer for appending and writes the buffer's capacity to + * *result_capacity. Guarantees *result_capacity>=min_capacity. + * May return a pointer to the caller-owned scratch buffer which must have + * scratch_capacity>=min_capacity. + * The returned buffer is only valid until the next operation + * on this ByteSink. + * + * After writing at most *result_capacity bytes, call Append() with the + * pointer returned from this function and the number of bytes written. + * Many Append() implementations will avoid copying bytes if this function + * returned an internal buffer. + * + * Partial usage example: + * int32_t capacity; + * char* buffer = sink->GetAppendBuffer(..., &capacity); + * ... Write n bytes into buffer, with n <= capacity. + * sink->Append(buffer, n); + * In many implementations, that call to Append will avoid copying bytes. + * + * If the ByteSink allocates or reallocates an internal buffer, it should use + * the desired_capacity_hint if appropriate. + * If a caller cannot provide a reasonable guess at the desired capacity, + * it should pass desired_capacity_hint=0. + * + * If a non-scratch buffer is returned, the caller may only pass + * a prefix to it to Append(). + * That is, it is not correct to pass an interior pointer to Append(). + * + * The default implementation always returns the scratch buffer. + * + * @param min_capacity required minimum capacity of the returned buffer; + * must be non-negative + * @param desired_capacity_hint desired capacity of the returned buffer; + * must be non-negative + * @param scratch default caller-owned buffer + * @param scratch_capacity capacity of the scratch buffer + * @param result_capacity pointer to an integer which will be set to the + * capacity of the returned buffer + * @return a buffer with *result_capacity>=min_capacity + * @stable ICU 4.2 + */ + virtual char* GetAppendBuffer(int32_t min_capacity, + int32_t desired_capacity_hint, + char* scratch, int32_t scratch_capacity, + int32_t* result_capacity); + + /** + * Flush internal buffers. + * Some byte sinks use internal buffers or provide buffering + * and require calling Flush() at the end of the stream. + * The ByteSink should be ready for further Append() calls after Flush(). + * The default implementation of Flush() does nothing. + * @stable ICU 4.2 + */ + virtual void Flush(); + +private: + ByteSink(const ByteSink &) = delete; + ByteSink &operator=(const ByteSink &) = delete; +}; + +// ------------------------------------------------------------- +// Some standard implementations + +/** + * Implementation of ByteSink that writes to a flat byte array, + * with bounds-checking: + * This sink will not write more than capacity bytes to outbuf. + * If more than capacity bytes are Append()ed, then excess bytes are ignored, + * and Overflowed() will return true. + * Overflow does not cause a runtime error. + * @stable ICU 4.2 + */ +class U_COMMON_API CheckedArrayByteSink : public ByteSink { +public: + /** + * Constructs a ByteSink that will write to outbuf[0..capacity-1]. + * @param outbuf buffer to write to + * @param capacity size of the buffer + * @stable ICU 4.2 + */ + CheckedArrayByteSink(char* outbuf, int32_t capacity); + /** + * Destructor. + * @stable ICU 4.2 + */ + virtual ~CheckedArrayByteSink(); + /** + * Returns the sink to its original state, without modifying the buffer. + * Useful for reusing both the buffer and the sink for multiple streams. + * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0 + * and Overflowed()=false. + * @return *this + * @stable ICU 4.6 + */ + virtual CheckedArrayByteSink& Reset(); + /** + * Append "bytes[0,n-1]" to this. + * @param bytes the pointer to the bytes + * @param n the number of bytes; must be non-negative + * @stable ICU 4.2 + */ + virtual void Append(const char* bytes, int32_t n) override; + /** + * Returns a writable buffer for appending and writes the buffer's capacity to + * *result_capacity. For details see the base class documentation. + * @param min_capacity required minimum capacity of the returned buffer; + * must be non-negative + * @param desired_capacity_hint desired capacity of the returned buffer; + * must be non-negative + * @param scratch default caller-owned buffer + * @param scratch_capacity capacity of the scratch buffer + * @param result_capacity pointer to an integer which will be set to the + * capacity of the returned buffer + * @return a buffer with *result_capacity>=min_capacity + * @stable ICU 4.2 + */ + virtual char* GetAppendBuffer(int32_t min_capacity, + int32_t desired_capacity_hint, + char* scratch, int32_t scratch_capacity, + int32_t* result_capacity) override; + /** + * Returns the number of bytes actually written to the sink. + * @return number of bytes written to the buffer + * @stable ICU 4.2 + */ + int32_t NumberOfBytesWritten() const { return size_; } + /** + * Returns true if any bytes were discarded, i.e., if there was an + * attempt to write more than 'capacity' bytes. + * @return true if more than 'capacity' bytes were Append()ed + * @stable ICU 4.2 + */ + UBool Overflowed() const { return overflowed_; } + /** + * Returns the number of bytes appended to the sink. + * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten() + * else they return the same number. + * @return number of bytes written to the buffer + * @stable ICU 4.6 + */ + int32_t NumberOfBytesAppended() const { return appended_; } +private: + char* outbuf_; + const int32_t capacity_; + int32_t size_; + int32_t appended_; + UBool overflowed_; + + CheckedArrayByteSink() = delete; + CheckedArrayByteSink(const CheckedArrayByteSink &) = delete; + CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete; +}; + +/** + * Implementation of ByteSink that writes to a "string". + * The StringClass is usually instantiated with a std::string. + * @stable ICU 4.2 + */ +template<typename StringClass> +class StringByteSink : public ByteSink { + public: + /** + * Constructs a ByteSink that will append bytes to the dest string. + * @param dest pointer to string object to append to + * @stable ICU 4.2 + */ + StringByteSink(StringClass* dest) : dest_(dest) { } + /** + * Constructs a ByteSink that reserves append capacity and will append bytes to the dest string. + * + * @param dest pointer to string object to append to + * @param initialAppendCapacity capacity beyond dest->length() to be reserve()d + * @stable ICU 60 + */ + StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) { + if (initialAppendCapacity > 0 && + (uint32_t)initialAppendCapacity > (dest->capacity() - dest->length())) { + dest->reserve(dest->length() + initialAppendCapacity); + } + } + /** + * Append "bytes[0,n-1]" to this. + * @param data the pointer to the bytes + * @param n the number of bytes; must be non-negative + * @stable ICU 4.2 + */ + virtual void Append(const char* data, int32_t n) override { dest_->append(data, n); } + private: + StringClass* dest_; + + StringByteSink() = delete; + StringByteSink(const StringByteSink &) = delete; + StringByteSink &operator=(const StringByteSink &) = delete; +}; + +U_NAMESPACE_END + +#endif /* U_SHOW_CPLUSPLUS_API */ + +#endif // __BYTESTREAM_H__ |