8000 closes bpo-45479: Degunkify Py_UniversalNewlineFgets. by benjaminp · Pull Request #28965 · python/cpython · GitHub
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closes bpo-45479: Degunkify Py_UniversalNewlineFgets. #28965

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Merged
merged 1 commit into from
Oct 15, 2021
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closes bpo-45479: Degunkify Py_UniversalNewlineFgets. #28965

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37 changes: 5 additions & 32 deletions Objects/fileobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -239,13 +239,7 @@ _PyLong_FileDescriptor_Converter(PyObject *o, void *ptr)
** Py_UniversalNewlineFgets is an fgets variation that understands
** all of \r, \n and \r\n conventions.
** The stream should be opened in binary mode.
** If fobj is NULL the routine always does newline conversion, and
** it may peek one char ahead to gobble the second char in \r\n.
** If fobj is non-NULL it must be a PyFileObject. In this case there
** is no readahead but in stead a flag is used to skip a following
** \n on the next read. Also, if the file is open in binary mode
** the whole conversion is skipped. Finally, the routine keeps track of
** the different types of newlines seen.
** The fobj parameter exists solely for legacy reasons and must be NULL.
** Note that we need no error handling: fgets() treats error and eof
** identically.
*/
Expand All @@ -254,32 +248,22 @@ Py_UniversalNewlineFgets(char *buf, int n, FILE *stream, PyObject *fobj)
{
char *p = buf;
int c;
int newlinetypes = 0;
int skipnextlf = 0;

if (fobj) {
errno = ENXIO; /* What can you do... */
return NULL;
}
FLOCKFILE(stream);
c = 'x'; /* Shut up gcc warning */
while (--n > 0 && (c = GETC(stream)) != EOF ) {
if (skipnextlf ) {
if (skipnextlf) {
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This block never executes. skipnextlf is only set if c == '\r' in the next block, in which case c is set to '\n', and the execution flow breaks out of the loop via if (c == '\n') break. The value of skipnextlf is handled after the loop. The loop can be simplified as follows:

    while (--n > 0 && (c = GETC(stream)) != EOF) {
        if (c == '\r') {
            /* Translate \r to \n, and skip an adjacent \n, if any. */
            skipnextlf = 1;
            c = '\n';
        }
        *p++ = c;
        if (c == '\n') {
            break;
        }
    }

skipnextlf = 0;
if (c == '\n') {
/* Seeing a \n here with skipnextlf true
** means we saw a \r before.
*/
newlinetypes |= NEWLINE_CRLF;
c = GETC(stream);
if (c == EOF) break;
} else {
/*
** Note that c == EOF also brings us here,
** so we're okay if the last char in the file
** is a CR.
*/
newlinetypes |= NEWLINE_CR;
}
}
if (c == '\r') {
Expand All @@ -289,26 +273,15 @@ Py_UniversalNewlineFgets(char *buf, int n, FILE *stream, PyObject *fobj)
*/
skipnextlf = 1;
c = '\n';
} else if ( c == '\n') {
newlinetypes |= NEWLINE_LF;
}
*p++ = c;
if (c == '\n') break;
}
/* if ( c == EOF && skipnextlf )
newlinetypes |= NEWLINE_CR; */
FUNLOCKFILE(stream);
*p = '\0';
if ( skipnextlf ) {
/* If we have no file object we cannot save the
** skipnextlf flag. We have to readahead, which
** will cause a pause if we're reading from an
** interactive stream, but that is very unlikely
** unless we're doing something silly like
** exec(open("/dev/tty").read()).
*/
c = GETC(stream);
if ( c != '\n' )
if (skipnextlf) {
int c = GETC(stream);
if (c != '\n')
ungetc(c, stream);
}
if (p == buf)
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