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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119//// setvbuf.cpp//// Copyright (c) Microsoft Corporation. All rights reserved.//// Defines setvbuf(), which is used to set buffering mode for a stream.//#include <corecrt_internal_stdio.h>#include <corecrt_internal_ptd_propagation.h>
// Helper for setvbuf() that sets various buffer properties and return zero.static int __cdecl set_buffer( __crt_stdio_stream const stream, _In_reads_opt_(buffer_size_in_bytes) char* const buffer, size_t const buffer_size_in_bytes, int const new_flag_bits ) throw(){ stream.set_flags(new_flag_bits); stream->_bufsiz = static_cast<int>(buffer_size_in_bytes); stream->_ptr = buffer; stream->_base = buffer; stream->_cnt = 0;
return 0;}
// Controls buffering and buffer size for the specified stream. The array// pointed to by 'buffer' is used as a buffer for the stream. If 'buffer' is// null, the CRT allocates a buffer of the requested size. The 'type' specifies// the type of buffering, which must be one of _IONBF (no buffering) or _IOLBF// or _IOFBF (both of which mean full buffering).//// Returns zero on success; nonzero on failure.static int __cdecl _setvbuf_internal( FILE* const public_stream, char* const buffer, int const type, size_t const buffer_size_in_bytes, __crt_cached_ptd_host& ptd ){ __crt_stdio_stream const stream(public_stream);
_UCRT_VALIDATE_RETURN(ptd, stream.valid(), EINVAL, -1);
// Make sure 'type' is one of the three allowed values, and if we are // buffering, make sure the size is between 2 and INT_MAX: _UCRT_VALIDATE_RETURN(ptd, type == _IONBF || type == _IOFBF || type == _IOLBF, EINVAL, -1);
if (type == _IOFBF || type == _IOLBF) { _UCRT_VALIDATE_RETURN(ptd, 2 <= buffer_size_in_bytes && buffer_size_in_bytes <= INT_MAX, EINVAL, -1); }
return __acrt_lock_stream_and_call(stream.public_stream(), [&] { // Force the buffer size to be even by masking the low order bit: size_t const usable_buffer_size = buffer_size_in_bytes & ~static_cast<size_t>(1);
// Flush the current buffer and free it, if it is ours: __acrt_stdio_flush_nolock(stream.public_stream(), ptd); __acrt_stdio_free_buffer_nolock(stream.public_stream());
// Clear the stream state bits related to buffering. Most of these // should never be set when setvbuf() is called, but it doesn't cost // anything to be safe. stream.unset_flags(_IOBUFFER_CRT | _IOBUFFER_USER | _IOBUFFER_NONE | _IOBUFFER_SETVBUF | _IOBUFFER_STBUF | _IOCTRLZ);
// Case 1: No buffering: if (type & _IONBF) { return set_buffer(stream, reinterpret_cast<char*>(&stream->_charbuf), 2, _IOBUFFER_NONE); }
// Cases 2 and 3 (below) cover the _IOFBF and _IOLBF types of buffering. // Line buffering is treated the same as full buffering, so the _IOLBF // bit in the flag is never set. Finally, since _IOFBF is defined to // be zero, full buffering is simply assumed whenever _IONBF is not set.
// Case 2: Default buffering, CRT-allocated buffer: if (buffer == nullptr) { char* const crt_buffer = _calloc_crt_t(char, usable_buffer_size).detach(); if (!crt_buffer) { #ifndef CRTDLL // Force library pre-termination procedure (this is placed here // because the code path should almost never be hit): ++_cflush; #endif
return -1; }
return set_buffer(stream, crt_buffer, usable_buffer_size, _IOBUFFER_CRT | _IOBUFFER_SETVBUF); }
// Case 3: Default buffering, user-provided buffer: return set_buffer(stream, buffer, usable_buffer_size, _IOBUFFER_USER | _IOBUFFER_SETVBUF); });}
extern "C" int __cdecl setvbuf( FILE* const public_stream, char* const buffer, int const type, size_t const buffer_size_in_bytes ){ __crt_cached_ptd_host ptd; return _setvbuf_internal(public_stream, buffer, type, buffer_size_in_bytes, ptd);}