From 1d3811f6498b4a7680c5c80300cbe3d0dbc77609 Mon Sep 17 00:00:00 2001 From: Daniel Jacobowitz Date: Sun, 16 Dec 2007 22:57:06 +0000 Subject: [PATCH] * gdb.texinfo (Overview): Clarify run-length encoding example. Remove the restriction on "+" and "-" characters. --- gdb/doc/ChangeLog | 5 +++++ gdb/doc/gdb.texinfo | 30 +++++++++++++++++------------- 2 files changed, 22 insertions(+), 13 deletions(-) diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog index f1c0f359c9..c1150b8c1a 100644 --- a/gdb/doc/ChangeLog +++ b/gdb/doc/ChangeLog @@ -1,3 +1,8 @@ +2007-12-16 Daniel Jacobowitz + + * gdb.texinfo (Overview): Clarify run-length encoding + example. Remove the restriction on "+" and "-" characters. + 2007-12-15 Eli Zaretskii * gdb.texinfo (Host I/O Packets): Fix xref syntax. diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 01f5db5098..36f1dc44b5 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -23158,20 +23158,24 @@ must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it is not interpreted as the start of a run-length encoded sequence (described next). -Response @var{data} can be run-length encoded to save space. A @samp{*} -means that the next character is an @sc{ascii} encoding giving a repeat count -which stands for that many repetitions of the character preceding the -@samp{*}. The encoding is @code{n+29}, yielding a printable character -where @code{n >=3} (which is where rle starts to win). The printable -characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric -value greater than 126 should not be used. +Response @var{data} can be run-length encoded to save space. +Run-length encoding replaces runs of identical characters with one +instance of the repeated character, followed by a @samp{*} and a +repeat count. The repeat count is itself sent encoded, to avoid +binary characters in @var{data}: a value of @var{n} is sent as +@code{@var{n}+29}. For a repeat count greater or equal to 3, this +produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii} +code 32) for a repeat count of 3. (This is because run-length +encoding starts to win for counts 3 or more.) Thus, for example, +@samp{0* } is a run-length encoding of ``0000'': the space character +after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 = +3}} more times. -So: -@smallexample -"@code{0* }" -@end smallexample -@noindent -means the same as "0000". +The printable characters @samp{#} and @samp{$} or with a numeric value +greater than 126 must not be used. Runs of six repeats (@samp{#}) or +seven repeats (@samp{$}) can be expanded using a repeat count of only +five (@samp{"}). For example, @samp{00000000} can be encoded as +@samp{0*"00}. The error response returned for some packets includes a two character error number. That number is not well defined.