STRING(3) STRING(3)
NAME
s_alloc, s_append, s_array, s_copy, s_error, s_free,
s_incref, s_memappend, s_nappend, s_new, s_newalloc,
s_parse, s_reset, s_restart, s_terminate, s_tolower, s_putc,
s_unique, s_grow, s_read, s_read_line, s_getline,
s_allocinstack, s_freeinstack, s_rdinstack - extensible
strings
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <String.h>
String* s_new(void)
void s_free(String *s)
String* s_newalloc(int n)
String* s_array(char *p, int n)
String* s_grow(String *s, int n)
void s_putc(String *s, int c)
void s_terminate(String *s)
String* s_reset(String *s)
String* s_restart(String *s)
String* s_append(String *s, char *p)
String* s_nappend(String *s, char *p, int n)
String* s_memappend(String *s, char *p, int n)
String* s_copy(char *p)
String* s_parse(String *s1, String *s2)
void s_tolower(String *s)
String* s_incref(String *s)
String* s_unique(String *s)
Sinstack* s_allocinstack(char *file)
void s_freeinstack(Sinstack *stack)
char* s_rdinstack(Sinstack *stack, String *s)
#include <bio.h>
int s_read(Biobuf *b, String *s, int n)
char* s_read_line(Biobuf *b, String *s)
char* s_getline(Biobuf *b, String *s)
DESCRIPTION
These routines manipulate extensible strings. The basic type
is String, which points to an array of characters. The
string maintains pointers to the beginning and end of the
allocated array. In addition a finger pointer keeps track
of where parsing will start (for s_parse) or new characters
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STRING(3) STRING(3)
will be added (for s_putc, s_append, and s_nappend). The
structure, and a few useful macros are:
typedef struct String {
Lock;
char*base;/* base of String */
char*end;/* end of allocated space+1 */
char*ptr;/* ptr into String */
...
} String;
#define s_to_c(s) ((s)->base)
#define s_len(s) ((s)->ptr-(s)->base)
#define s_clone(s) s_copy((s)->base)
S_to_c is used when code needs a reference to the character
array. Using s->base directly is frowned upon since it
exposes too much of the implementation.
Allocation and freeing
A string must be allocated before it can be used. One nor-
mally does this using s_new, giving the string an initial
allocation of 128 bytes. If you know that the string will
need to grow much longer, you can use s_newalloc instead,
specifying the number of bytes in the initial allocation.
S_free causes both the string and its character array to be
freed.
S_grow grows a string's allocation by a fixed amount. It is
useful if you are reading directly into a string's character
array but should be avoided if possible.
S_array is used to create a constant array, that is, one
whose contents won't change. It points directly to the
character array given as an argument. Tread lightly when
using this call.
Filling the string
After its initial allocation, the string points to the
beginning of an allocated array of characters starting with
NUL.
S_putc writes a character into the string at the pointer and
advances the pointer to point after it.
S_terminate writes a NUL at the pointer but doesn't advance
it.
S_restart resets the pointer to the begining of the string
but doesn't change the contents.
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STRING(3) STRING(3)
S_reset is equivalent to s_restart followed by s_terminate.
S_append and s_nappend copy characters into the string at
the pointer and advance the pointer. They also write a NUL
at the pointer without advancing the pointer beyond it.
Both routines stop copying on encountering a NUL.
S_memappend is like s_nappend but doesn't stop at a NUL.
If you know the initial character array to be copied into a
string, you can allocate a string and copy in the bytes
using s_copy. This is the equivalent of a s_new followed by
an s_append.
S_parse copies the next white space terminated token from s1
to the end of s2. White space is defined as space, tab, and
newline. Both single and double quoted strings are treated
as a single token. The bounding quotes are not copied.
There is no escape mechanism.
S_tolower converts all ASCII characters in the string to
lower case.
Multithreading
S_incref is used by multithreaded programs to avoid having
the string memory released until the last user of the string
performs an s_free. S_unique returns a unique copy of the
string: if the reference count it 1 it returns the string,
otherwise it returns an s_clone of the string.
Bio interaction
S_read reads the requested number of characters through a
Biobuf into a string. The string is grown as necessary. An
eof or error terminates the read. The number of bytes read
is returned. The string is null terminated.
S_read_line reads up to and including the next newline and
returns a pointer to the beginning of the bytes read. An
eof or error terminates the read. The string is null termi-
nated.
S_getline reads up to the next newline, appends the input to
s, and returns a pointer to the beginning of the bytes read.
Leading spaces and tabs and the trailing newline are all
discarded. S_getline discards blank lines and lines begin-
ning with `#'. S_getline ignores newlines escaped by
immediately-preceding backslashes.
S_allocinstack allocates an input stack with the single file
file open for reading. S_freeinstack frees an input stack.
S_rdinstack reads a line from an input stack. It follows
the same rules as s_getline except that when it encounters a
line of the form #include newfile, s_getline pushes newfile
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STRING(3) STRING(3)
onto the input stack, postponing further reading of the cur-
rent file until newfile has been read. The input stack has
a maximum depth of 32 nested include files.
SOURCE
/usr/local/plan9/src/libString
SEE ALSO
bio(3)
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