diff options
| -rw-r--r-- | Doc/lib/libstdtypes.tex | 31 | ||||
| -rw-r--r-- | Lib/test/test_largefile.py | 24 | ||||
| -rw-r--r-- | Objects/fileobject.c | 67 |
3 files changed, 73 insertions, 49 deletions
diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex index 27f1c52..2bd6420 100644 --- a/Doc/lib/libstdtypes.tex +++ b/Doc/lib/libstdtypes.tex @@ -161,7 +161,7 @@ only by sequence types (below). \subsection{Numeric Types \label{typesnumeric}} -There are four numeric types: \dfn{plain integers}, \dfn{long integers}, +There are four numeric types: \dfn{plain integers}, \dfn{long integers}, \dfn{floating point numbers}, and \dfn{complex numbers}. Plain integers (also just called \dfn{integers}) are implemented using \ctype{long} in C, which gives them at least 32 @@ -178,7 +178,7 @@ working with. Complex numbers have a real and imaginary part, which are both implemented using \ctype{double} in C. To extract these parts from -a complex number \var{z}, use \code{\var{z}.real} and \code{\var{z}.imag}. +a complex number \var{z}, use \code{\var{z}.real} and \code{\var{z}.imag}. Numbers are created by numeric literals or as the result of built-in functions and operators. Unadorned integer literals (including hex @@ -248,7 +248,7 @@ Notes: \item[(1)] For (plain or long) integer division, the result is an integer. -The result is always rounded towards minus infinity: 1/2 is 0, +The result is always rounded towards minus infinity: 1/2 is 0, (-1)/2 is -1, 1/(-2) is -1, and (-1)/(-2) is 0. Note that the result is a long integer if either operand is a long integer, regardless of the numeric value. @@ -472,7 +472,7 @@ Notes: the end of the string: \code{len(\var{s}) + \var{i}} or \code{len(\var{s}) + \var{j}} is substituted. But note that \code{-0} is still \code{0}. - + \item[(3)] The slice of \var{s} from \var{i} to \var{j} is defined as the sequence of items with index \var{k} such that \code{\var{i} <= \var{k} < \var{j}}. If \var{i} or \var{j} is greater than @@ -808,7 +808,7 @@ are replaced by \code{\%g} conversions.\footnote{ Additional string operations are defined in standard modules \refmodule{string}\refstmodindex{string} and -\refmodule{re}.\refstmodindex{re} +\refmodule{re}.\refstmodindex{re} \subsubsection{XRange Type \label{typesseq-xrange}} @@ -881,7 +881,7 @@ Notes: no longer works in Python 2.0. Use of this misfeature has been deprecated since Python 1.4. -\item[(2)] Raises an exception when \var{x} is not a list object. The +\item[(2)] Raises an exception when \var{x} is not a list object. The \method{extend()} method is experimental and not supported by mutable sequence types other than lists. @@ -1034,7 +1034,7 @@ over a dictionary, as often used in set algorithms. File objects\obindex{file} are implemented using C's \code{stdio} package and can be created with the built-in constructor -\function{file()}\bifuncindex{file} described in section +\function{file()}\bifuncindex{file} described in section \ref{built-in-funcs}, ``Built-in Functions.''\footnote{\function{file()} is new in Python 2.2. The older built-in \function{open()} is an alias for \function{file()}.} @@ -1100,10 +1100,10 @@ Files have the following methods: \begin{methoddesc}[file]{readline}{\optional{size}} Read one entire line from the file. A trailing newline character is kept in the string\footnote{ - The advantage of leaving the newline on is that an empty string - can be returned to mean \EOF{} without being ambiguous. Another - advantage is that (in cases where it might matter, for example. if you - want to make an exact copy of a file while scanning its lines) + The advantage of leaving the newline on is that an empty string + can be returned to mean \EOF{} without being ambiguous. Another + advantage is that (in cases where it might matter, for example. if you + want to make an exact copy of a file while scanning its lines) you can tell whether the last line of a file ended in a newline or not (yes this happens!). } (but may be absent when a file ends with an @@ -1152,9 +1152,14 @@ Files have the following methods: \end{methoddesc} \begin{methoddesc}[file]{truncate}{\optional{size}} - Truncate the file's size. If the optional \var{size} argument + Truncate the file's size. If the optional \var{size} argument is present, the file is truncated to (at most) that size. The size - defaults to the current position. + defaults to the current position. The current file position is + not changed. Note that if a specified size exceeds the file's + current size, the result is platform-dependent: possibilities + include that file may remain unchanged, increase to the specified + size as if zero-filled, or increase to the specified size with + undefined new content. Availability: Windows, many \UNIX variants. \end{methoddesc} diff --git a/Lib/test/test_largefile.py b/Lib/test/test_largefile.py index bc24635..8bff5df 100644 --- a/Lib/test/test_largefile.py +++ b/Lib/test/test_largefile.py @@ -133,24 +133,30 @@ if hasattr(f, 'truncate'): print 'try truncate' f = open(name, 'r+b') f.seek(0, 2) - expect(f.tell(), size+1) + expect(f.tell(), size+1) # else we've lost track of the true size # Cut it back via seek + truncate with no argument. newsize = size - 10 f.seek(newsize) f.truncate() - expect(f.tell(), newsize) - # Ensure that truncate(bigger than true size) doesn't grow the file. - f.truncate(size) - expect(f.tell(), newsize) + expect(f.tell(), newsize) # else pointer moved + f.seek(0, 2) + expect(f.tell(), newsize) # else wasn't truncated # Ensure that truncate(smaller than true size) shrinks the file. newsize -= 1 - f.seek(0) + f.seek(42) f.truncate(newsize) - expect(f.tell(), newsize) + expect(f.tell(), 42) # else pointer moved + f.seek(0, 2) + expect(f.tell(), newsize) # else wasn't truncated + + # XXX truncate(larger than true size) is ill-defined across platforms + # cut it waaaaay back - f.truncate(1) f.seek(0) - expect(len(f.read()), 1) + f.truncate(1) + expect(f.tell(), 0) # else pointer moved + expect(len(f.read()), 1) # else wasn't truncated + f.close() os.unlink(name) diff --git a/Objects/fileobject.c b/Objects/fileobject.c index f2f5dcf..7bcc82a 100644 --- a/Objects/fileobject.c +++ b/Objects/fileobject.c @@ -415,46 +415,59 @@ file_truncate(PyFileObject *f, PyObject *args) #ifdef MS_WIN32 /* MS _chsize doesn't work if newsize doesn't fit in 32 bits, - so don't even try using it. truncate() should never grow the - file, but MS SetEndOfFile will grow a file, so we need to - compare the specified newsize to the actual size. Some - optimization could be done here when newsizeobj is NULL. */ + so don't even try using it. */ { - Py_off_t currentEOF; /* actual size */ + Py_off_t current; /* current file position */ HANDLE hFile; int error; - /* First move to EOF, and set currentEOF to the size. */ - errno = 0; - if (_portable_fseek(f->f_fp, 0, SEEK_END) != 0) - goto onioerror; - errno = 0; - currentEOF = _portable_ftell(f->f_fp); - if (currentEOF == -1) - goto onioerror; - - if (newsize > currentEOF) - newsize = currentEOF; /* never grow the file */ - - /* Move to newsize, and truncate the file there. */ - if (newsize != currentEOF) { + /* current <- current file postion. */ + if (newsizeobj == NULL) + current = newsize; + else { + Py_BEGIN_ALLOW_THREADS errno = 0; - if (_portable_fseek(f->f_fp, newsize, SEEK_SET) != 0) + current = _portable_ftell(f->f_fp); + Py_END_ALLOW_THREADS + if (current == -1) goto onioerror; + } + + /* Move to newsize. */ + if (current != newsize) { Py_BEGIN_ALLOW_THREADS errno = 0; - hFile = (HANDLE)_get_osfhandle(fileno(f->f_fp)); - error = hFile == (HANDLE)-1; - if (!error) { - error = SetEndOfFile(hFile) == 0; - if (error) - errno = EACCES; - } + error = _portable_fseek(f->f_fp, newsize, SEEK_SET) + != 0; Py_END_ALLOW_THREADS if (error) goto onioerror; } + /* Truncate. Note that this may grow the file! */ + Py_BEGIN_ALLOW_THREADS + errno = 0; + hFile = (HANDLE)_get_osfhandle(fileno(f->f_fp)); + error = hFile == (HANDLE)-1; + if (!error) { + error = SetEndOfFile(hFile) == 0; + if (error) + errno = EACCES; + } + Py_END_ALLOW_THREADS + if (error) + goto onioerror; + + /* Restore original file position. */ + if (current != newsize) { + Py_BEGIN_ALLOW_THREADS + errno = 0; + error = _portable_fseek(f->f_fp, current, SEEK_SET) + != 0; + Py_END_ALLOW_THREADS + if (error) + goto onioerror; + } } #else Py_BEGIN_ALLOW_THREADS |