2010/9/3 Jilles Tjoelker jil...@stack.nl:
This patch assumes that the file descriptor is discarded afterwards (its
position does not matter). Therefore the very common construct
while read x; do
...
done
stops working.
Ohh.. thanks for that, I didn't see it.
Actually while read x continues to work.
But reopening the file doesn't as in :
read a b datafile
echo ${a} ${b}
read a b datafile
echo ${a} ${b}
I attached an updated patch that corrects this pb by discarding the
buffer when opening a new file.
I also put everything in new files (bufreadcmd.c .h), in order to
ease its understanding.
--
Steve Schnepp
http://blog.pwkf.org/
A possible fix is to check first if the input supports seeking. If it
does, use the buffering and at the end of the line seek backwards for
the number of bytes remaining in the buffer. If it does not, read one
byte at a time.
--
Jilles Tjoelker
--
Steve Schnepp
http://blog.pwkf.org/
Common subdirectories: dash-0.5.4/src/bltin and dash-0.5.4-patched/src/bltin
diff -puN dash-0.5.4/src/bufreadcmd.c dash-0.5.4-patched/src/bufreadcmd.c
--- dash-0.5.4/src/bufreadcmd.c 1970-01-01 01:00:00.0 +0100
+++ dash-0.5.4-patched/src/bufreadcmd.c 2010-09-04 12:31:46.0 +0200
@@ -0,0 +1,59 @@
+/*
+ * Offers a buffered read builtin
+ */
+
+#include unistd.h
+#include stdlib.h
+
+#include bufreadcmd.h
+
+#ifdef BUF_READ_BUILTIN_DISABLED
+int dup2_wrapper(int old, int new) {
+ return dup2(old, new);
+}
+int read_stdin_bufferred(char *c) {
+ return read(0, buffer, 1);
+}
+#else // BUF_READ_BUILTIN_DISABLED
+
+/*
+ * Reads from fd 0, with a CHUNK_READ_SIZE,
+ * but emitting one char at a time
+ */
+#define CHUNK_READ_SIZE 32
+static char buffer[CHUNK_READ_SIZE];
+static int buffer_offset = 0;
+static int buffer_len = 0;
+
+int read_stdin_bufferred(char* c) {
+ if (buffer_len == 0) {
+ // No caracter left, resetting buffer read some more
+ buffer_offset = 0;
+ buffer_len = read(0, buffer, CHUNK_READ_SIZE);
+
+ if (buffer_len == 0) {
+ // Nothing to read anymore
+ return 0;
+ }
+ }
+
+ // Still some character left
+ *c = buffer[buffer_offset++];
+ buffer_len--;
+
+ return 1;
+}
+
+static void _flush_readcmd(int fd) {
+ if (fd == 0) {
+ // Flush the buffer, discarding its content
+ buffer_len = 0;
+ }
+}
+
+/* Intercept dup2() calls */
+int dup2_wrapper(int old, int new) {
+ _flush_readcmd(new);
+ return dup2(old, new);
+}
+#endif // BUF_READ_BUILTIN_DISABLED
diff -puN dash-0.5.4/src/bufreadcmd.h dash-0.5.4-patched/src/bufreadcmd.h
--- dash-0.5.4/src/bufreadcmd.h 1970-01-01 01:00:00.0 +0100
+++ dash-0.5.4-patched/src/bufreadcmd.h 2010-09-04 12:23:53.0 +0200
@@ -0,0 +1,3 @@
+/* Used for flushing the readcmd read() buffer */
+int dup2_wrapper(int to, int from);
+int read_stdin_bufferred(char *c);
Common subdirectories: dash-0.5.4/src/.deps and dash-0.5.4-patched/src/.deps
diff -puN dash-0.5.4/src/eval.c dash-0.5.4-patched/src/eval.c
--- dash-0.5.4/src/eval.c 2007-07-13 10:26:42.0 +0200
+++ dash-0.5.4-patched/src/eval.c 2010-09-04 12:24:55.0 +0200
@@ -64,6 +64,8 @@
#include myhistedit.h
#endif
+#include bufreadcmd.h
+
/* flags in argument to evaltree */
#define EV_EXIT 01 /* exit after evaluating tree */
@@ -543,11 +545,12 @@ evalpipe(union node *n, int flags)
close(pip[0]);
}
if (prevfd 0) {
-dup2(prevfd, 0);
+dup2_wrapper(prevfd, 0);
+
close(prevfd);
}
if (pip[1] 1) {
-dup2(pip[1], 1);
+dup2_wrapper(pip[1], 1);
close(pip[1]);
}
evaltreenr(lp-n, flags);
@@ -625,7 +628,7 @@ evalbackcmd(union node *n, struct backcm
FORCEINTON;
close(pip[0]);
if (pip[1] != 1) {
-dup2(pip[1], 1);
+dup2_wrapper(pip[1], 1);
close(pip[1]);
}
eflag = 0;
diff -puN dash-0.5.4/src/Makefile dash-0.5.4-patched/src/Makefile
--- dash-0.5.4/src/Makefile 2010-09-04 13:06:05.0 +0200
+++ dash-0.5.4-patched/src/Makefile 2010-09-04 13:08:26.0 +0200
@@ -57,7 +57,7 @@ am__objects_1 = alias.$(OBJEXT) arith_yy
miscbltin.$(OBJEXT) mystring.$(OBJEXT) options.$(OBJEXT) \
parser.$(OBJEXT) redir.$(OBJEXT) show.$(OBJEXT) trap.$(OBJEXT) \
output.$(OBJEXT) printf.$(OBJEXT) system.$(OBJEXT) \
- test.$(OBJEXT) times.$(OBJEXT) var.$(OBJEXT)
+ test.$(OBJEXT) times.$(OBJEXT) var.$(OBJEXT) bufreadcmd.$(OBJEXT)
am_dash_OBJECTS = $(am__objects_1) arith.$(OBJEXT)
dash_OBJECTS = $(am_dash_OBJECTS)
dash_DEPENDENCIES = builtins.o init.o nodes.o signames.o syntax.o
@@ -169,14 +169,14 @@ dash_CFILES = \
alias.c arith_yylex.c cd.c error.c eval.c exec.c expand.c \
histedit.c input.c jobs.c mail.c main.c memalloc.c miscbltin.c \
mystring.c options.c parser.c redir.c show.c trap.c output.c \
- bltin/printf.c system.c bltin/test.c bltin/times.c var.c
+ bltin/printf.c system.c bltin/test.c bltin/times.c var.c bufreadcmd.c
