| 1 | /////////////////////////////////////////////////////////////////////////////// |
| 2 | // Name: common/wxexec.cpp |
| 3 | // Purpose: defines wxStreamTempInputBuffer which is used by Unix and MSW |
| 4 | // implementations of wxExecute; this file is only used by the |
| 5 | // library and never by the user code |
| 6 | // Author: Vadim Zeitlin |
| 7 | // Modified by: |
| 8 | // Created: 20.08.02 |
| 9 | // RCS-ID: $Id$ |
| 10 | // Copyright: (c) 2002 Vadim Zeitlin <vadim@wxwindows.org> |
| 11 | // Licence: wxWindows licence |
| 12 | /////////////////////////////////////////////////////////////////////////////// |
| 13 | |
| 14 | #ifndef _WX_WXEXEC_CPP_ |
| 15 | #define _WX_WXEXEC_CPP_ |
| 16 | |
| 17 | // this file should never be compiled directly, just included by other code |
| 18 | #ifndef _WX_USED_BY_WXEXECUTE_ |
| 19 | #error "You should never directly build this file!" |
| 20 | #endif |
| 21 | |
| 22 | // ---------------------------------------------------------------------------- |
| 23 | // wxStreamTempInputBuffer |
| 24 | // ---------------------------------------------------------------------------- |
| 25 | |
| 26 | /* |
| 27 | wxStreamTempInputBuffer is a hack which we need to solve the problem of |
| 28 | executing a child process synchronously with IO redirecting: when we do |
| 29 | this, the child writes to a pipe we open to it but when the pipe buffer |
| 30 | (which has finite capacity, e.g. commonly just 4Kb) becomes full we have to |
| 31 | read data from it because the child blocks in its write() until then and if |
| 32 | it blocks we are never going to return from wxExecute() so we dead lock. |
| 33 | |
| 34 | So here is the fix: we now read the output as soon as it appears into a temp |
| 35 | buffer (wxStreamTempInputBuffer object) and later just stuff it back into |
| 36 | the stream when the process terminates. See supporting code in wxExecute() |
| 37 | itself as well. |
| 38 | |
| 39 | Note that this is horribly inefficient for large amounts of output (count |
| 40 | the number of times we copy the data around) and so a better API is badly |
| 41 | needed! However it's not easy to devise a way to do this keeping backwards |
| 42 | compatibility with the existing wxExecute(wxEXEC_SYNC)... |
| 43 | */ |
| 44 | |
| 45 | class wxStreamTempInputBuffer |
| 46 | { |
| 47 | public: |
| 48 | wxStreamTempInputBuffer(); |
| 49 | |
| 50 | // call to associate a stream with this buffer, otherwise nothing happens |
| 51 | // at all |
| 52 | void Init(wxPipeInputStream *stream); |
| 53 | |
| 54 | // check for input on our stream and cache it in our buffer if any |
| 55 | // |
| 56 | // return true if anything was done |
| 57 | bool Update(); |
| 58 | |
| 59 | ~wxStreamTempInputBuffer(); |
| 60 | |
| 61 | private: |
| 62 | // the stream we're buffering, if NULL we don't do anything at all |
| 63 | wxPipeInputStream *m_stream; |
| 64 | |
| 65 | // the buffer of size m_size (NULL if m_size == 0) |
| 66 | void *m_buffer; |
| 67 | |
| 68 | // the size of the buffer |
| 69 | size_t m_size; |
| 70 | |
| 71 | wxDECLARE_NO_COPY_CLASS(wxStreamTempInputBuffer); |
| 72 | }; |
| 73 | |
| 74 | inline wxStreamTempInputBuffer::wxStreamTempInputBuffer() |
| 75 | { |
| 76 | m_stream = NULL; |
| 77 | m_buffer = NULL; |
| 78 | m_size = 0; |
| 79 | } |
| 80 | |
| 81 | inline void wxStreamTempInputBuffer::Init(wxPipeInputStream *stream) |
| 82 | { |
| 83 | m_stream = stream; |
| 84 | } |
| 85 | |
| 86 | inline |
| 87 | bool wxStreamTempInputBuffer::Update() |
| 88 | { |
| 89 | if ( !m_stream || !m_stream->CanRead() ) |
| 90 | return false; |
| 91 | |
| 92 | // realloc in blocks of 4Kb: this is the default (and minimal) buffer |
| 93 | // size of the Unix pipes so it should be the optimal step |
| 94 | // |
| 95 | // NB: don't use "static int" in this inline function, some compilers |
| 96 | // (e.g. IBM xlC) don't like it |
| 97 | enum { incSize = 4096 }; |
| 98 | |
| 99 | void *buf = realloc(m_buffer, m_size + incSize); |
| 100 | if ( !buf ) |
| 101 | { |
| 102 | // don't read any more, we don't have enough memory to do it |
| 103 | m_stream = NULL; |
| 104 | } |
| 105 | else // got memory for the buffer |
| 106 | { |
| 107 | m_buffer = buf; |
| 108 | m_stream->Read((char *)m_buffer + m_size, incSize); |
| 109 | m_size += m_stream->LastRead(); |
| 110 | } |
| 111 | |
| 112 | return true; |
| 113 | } |
| 114 | |
| 115 | inline |
| 116 | wxStreamTempInputBuffer::~wxStreamTempInputBuffer() |
| 117 | { |
| 118 | if ( m_buffer ) |
| 119 | { |
| 120 | m_stream->Ungetch(m_buffer, m_size); |
| 121 | free(m_buffer); |
| 122 | } |
| 123 | } |
| 124 | |
| 125 | #endif // _WX_WXEXEC_CPP_ |
| 126 | |