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Fix typos and wording.

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This commit is contained in:
Ulrich Drepper 2001-08-12 16:44:22 +00:00
parent 5a5560f0f9
commit 3ca9e670b3
1 changed files with 9 additions and 8 deletions
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17
manual/stdio.texi
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@ -553,11 +553,11 @@ Now that we covered why it is necessary to have these locking it is
necessary to talk about situations when locking is unwanted and what can necessary to talk about situations when locking is unwanted and what can
be done. The locking operations (explicit or implicit) don't come for be done. The locking operations (explicit or implicit) don't come for
free. Even if a lock is not taken the cost is not zero. The operations free. Even if a lock is not taken the cost is not zero. The operations
which have to be performed require memory operations which are save in which have to be performed require memory operations that are safe in
multi-processor environments. With the many local caches involved in multi-processor environments. With the many local caches involved in
such systems this is quite costly. So it is best to avoid the locking such systems this is quite costly. So it is best to avoid the locking
completely if it is known that the code using the stream is never used completely if it is not needed -- because the code in question is never
in a context where more than one thread can use the stream at one time. used in a context where two or more threads may use a stream at a time.
This can be determined most of the time for application code; for This can be determined most of the time for application code; for
library code which can be used in many contexts one should default to be library code which can be used in many contexts one should default to be
conservative and use locking. conservative and use locking.
@ -566,15 +566,16 @@ There are two basic mechanisms to avoid locking. The first is to use
the @code{_unlocked} variants of the stream operations. The POSIX the @code{_unlocked} variants of the stream operations. The POSIX
standard defines quite a few of those and the GNU library adds a few standard defines quite a few of those and the GNU library adds a few
more. These variants of the functions behave just like the functions more. These variants of the functions behave just like the functions
with the name without the suffix except that they are not locking the with the name without the suffix except that they do not lock the
stream. Using these functions is very desirable since they are stream. Using these functions is very desirable since they are
potentially much faster. This is not only because the locking potentially much faster. This is not only because the locking
operation itself is avoided. More importantly, functions like operation itself is avoided. More importantly, functions like
@code{putc} and @code{getc} are very simple and traditionally (before the @code{putc} and @code{getc} are very simple and traditionally (before the
introduction of threads) were implemented as macros which are very fast introduction of threads) were implemented as macros which are very fast
if the buffer is not empty. With locking required these functions are if the buffer is not empty. With the addition of locking requirements
now no macros anymore (the code generated would be too much). But these these functions are no longer implemented as macros since they would
macros are still available with the same functionality under the new would expand to too much code.
But these macros are still available with the same functionality under the new
names @code{putc_unlocked} and @code{getc_unlocked}. This possibly huge names @code{putc_unlocked} and @code{getc_unlocked}. This possibly huge
difference of speed also suggests the use of the @code{_unlocked} difference of speed also suggests the use of the @code{_unlocked}
functions even if locking is required. The difference is that the functions even if locking is required. The difference is that the
@ -639,7 +640,7 @@ in @file{stdio_ext.h}.
This function is especially useful when program code has to be used This function is especially useful when program code has to be used
which is written without knowledge about the @code{_unlocked} functions which is written without knowledge about the @code{_unlocked} functions
(or if the programmer was to lazy to use them). (or if the programmer was too lazy to use them).
@node Streams and I18N @node Streams and I18N
@section Streams in Internationalized Applications @section Streams in Internationalized Applications