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sed,get_line_from_file: improve comments

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This commit is contained in:
Denis Vlasenko 2007-01-17 23:16:16 +00:00
parent ae114c235e
commit ef44d9d9f2
2 changed files with 30 additions and 19 deletions
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44
editors/sed.c
View File

@ -576,28 +576,33 @@ static void do_subst_w_backrefs(char *line, char *replace)
/* go through the replacement string */ /* go through the replacement string */
for (i = 0; replace[i]; i++) { for (i = 0; replace[i]; i++) {
/* if we find a backreference (\1, \2, etc.) print the backref'ed * text */ /* if we find a backreference (\1, \2, etc.) print the backref'ed * text */
if (replace[i] == '\\' && replace[i+1] >= '0' && replace[i+1] <= '9') { if (replace[i] == '\\') {
int backref = replace[++i]-'0'; unsigned backref = replace[++i] - '0';
if (backref <= 9) {
/* print out the text held in bbg.regmatch[backref] */ /* print out the text held in bbg.regmatch[backref] */
if (bbg.regmatch[backref].rm_so != -1) { if (bbg.regmatch[backref].rm_so != -1) {
j = bbg.regmatch[backref].rm_so; j = bbg.regmatch[backref].rm_so;
while (j < bbg.regmatch[backref].rm_eo) while (j < bbg.regmatch[backref].rm_eo)
pipe_putc(line[j++]); pipe_putc(line[j++]);
}
continue;
} }
/* I _think_ it is impossible to get '\' to be
* the last char in replace string. Thus we dont check
* for replace[i] == NUL. (counterexample anyone?) */
/* if we find a backslash escaped character, print the character */
pipe_putc(replace[i]);
continue;
} }
/* if we find a backslash escaped character, print the character */
else if (replace[i] == '\\') pipe_putc(replace[++i]);
/* if we find an unescaped '&' print out the whole matched text. */ /* if we find an unescaped '&' print out the whole matched text. */
else if (replace[i] == '&') { if (replace[i] == '&') {
j = bbg.regmatch[0].rm_so; j = bbg.regmatch[0].rm_so;
while (j < bbg.regmatch[0].rm_eo) while (j < bbg.regmatch[0].rm_eo)
pipe_putc(line[j++]); pipe_putc(line[j++]);
continue;
} }
/* Otherwise just output the character. */ /* Otherwise just output the character. */
else pipe_putc(replace[i]); pipe_putc(replace[i]);
} }
} }
@ -722,6 +727,9 @@ static char *get_next_line(int *last_char)
lc = 0; lc = 0;
flush_append(); flush_append();
while (bbg.current_input_file < bbg.input_file_count) { while (bbg.current_input_file < bbg.input_file_count) {
/* Read line up to a newline or NUL byte, inclusive,
* return malloc'ed char[]. length of the chunk read
* is stored in len. NULL if EOF/error */
temp = bb_get_chunk_from_file( temp = bb_get_chunk_from_file(
bbg.input_file_list[bbg.current_input_file], &len); bbg.input_file_list[bbg.current_input_file], &len);
if (temp) { if (temp) {
@ -753,7 +761,8 @@ static char *get_next_line(int *last_char)
* echo -n thingy >z1 * echo -n thingy >z1
* echo -n again >z2 * echo -n again >z2
* >znull * >znull
* sed "s/i/z/" z1 z2 znull | hexdump -vC output: * sed "s/i/z/" z1 z2 znull | hexdump -vC
* output:
* gnu sed 4.1.5: * gnu sed 4.1.5:
* 00000000 74 68 7a 6e 67 79 0a 61 67 61 7a 6e |thzngy.agazn| * 00000000 74 68 7a 6e 67 79 0a 61 67 61 7a 6e |thzngy.agazn|
* bbox: * bbox:
@ -771,8 +780,9 @@ static int puts_maybe_newline(char *s, FILE *file, int prev_last_char, int last_
last_puts_char = '\n'; last_puts_char = '\n';
} }
fputs(s, file); fputs(s, file);
/* 'x': we don't care what is it, but we know it isn't '\n' */ /* why 'x'? - just something which is not '\n' */
if (s[0]) last_puts_char = 'x'; if (s[0])
last_puts_char = 'x';
if (!(last_char & 0x100)) { /* had trailing '\n' or '\0'? */ if (!(last_char & 0x100)) { /* had trailing '\n' or '\0'? */
last_char &= 0xff; last_char &= 0xff;
fputc(last_char, file); fputc(last_char, file);

5
libbb/get_line_from_file.c
View File

@ -13,8 +13,9 @@
/* This function reads an entire line from a text file, up to a newline /* This function reads an entire line from a text file, up to a newline
* or NUL byte, inclusive. It returns a malloc'ed char * which must be * or NUL byte, inclusive. It returns a malloc'ed char * which must be
* stored and free'ed by the caller. If end is null '\n' isn't considered * stored and free'ed by the caller. If end is NULL '\n' isn't considered
* end of line. If end isn't null, length of the chunk read is stored in it. */ * end of line. If end isn't NULL, length of the chunk read is stored in it.
* Return NULL if EOF/error */
char *bb_get_chunk_from_file(FILE * file, int *end) char *bb_get_chunk_from_file(FILE * file, int *end)
{ {