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| author | Thien-Thi Nguyen <ttn@gnuvola.org> | 2006-05-27 00:49:32 +0000 |
|---|---|---|
| committer | Thien-Thi Nguyen <ttn@gnuvola.org> | 2006-05-27 00:49:32 +0000 |
| commit | f1b64ef1e59bad4490248e41da92affdca31e7ac (patch) | |
| tree | 1de6b8f8c3bd47b75c2bf4704934fd18c0c7b332 | |
| parent | 27af5d58f03d7792b0942cd1d57524f5fc8e469f (diff) | |
| download | emacs-f1b64ef1e59bad4490248e41da92affdca31e7ac.tar.gz | |
(Bindat Functions): Explain term "total length".
Use it in `bindat-length' and `bindat-pack' descriptions.
| -rw-r--r-- | lispref/ChangeLog | 5 | ||||
| -rw-r--r-- | lispref/processes.texi | 16 |
2 files changed, 18 insertions, 3 deletions
diff --git a/lispref/ChangeLog b/lispref/ChangeLog index a4bbd6b535e..53f5fd597af 100644 --- a/lispref/ChangeLog +++ b/lispref/ChangeLog @@ -1,3 +1,8 @@ +2006-05-27 Thien-Thi Nguyen <ttn@gnu.org> + + * processes.texi (Bindat Functions): Explain term "total length". + Use it in bindat-length and bindat-pack descriptions. + 2006-05-26 Eli Zaretskii <eliz@gnu.org> * tips.texi (Coding Conventions): Advise against using diff --git a/lispref/processes.texi b/lispref/processes.texi index 501c4a65c57..64b5bdd77bd 100644 --- a/lispref/processes.texi +++ b/lispref/processes.texi @@ -2268,10 +2268,17 @@ field @code{c} in the third element of subfield @code{b} of field @code{a}. (This corresponds to @code{struct.a.b[2].c} in C.) @end defun + Although packing and unpacking operations change the organization of +data (in memory), they preserve the data's @dfn{total length}, which is +the sum of all the fields' lengths, in bytes. This value is not +generally inherent in either the specification or alist alone; instead, +both pieces of information contribute to its calculation. Likewise, the +length of a string or array being unpacked may be longer than the data's +total length as described by the specification. + @defun bindat-length spec struct -@c ??? I don't understand this at all -- rms -This function returns the length in bytes of @var{struct}, according -to @var{spec}. +This function returns the total length of the data in @var{struct}, +according to @var{spec}. @end defun @defun bindat-pack spec struct &optional raw-data pos @@ -2281,6 +2288,9 @@ new byte array starting at the beginning. However, if @var{raw-data} is non-@code{nil}, it specifies a pre-allocated unibyte string or vector to pack into. If @var{pos} is non-@code{nil}, it specifies the starting offset for packing into @code{raw-data}. + +When pre-allocating, you should make sure @code{(length @var{raw-data})} +meets or exceeds the total length to avoid an out-of-range error. @end defun @defun bindat-ip-to-string ip |