ref: 17b3ae4f1a1ce71b26bd2d383c9be513af29bb66
dir: /xml/
.TH XML 2
.SH NAME
xmlattr,
xmlcalloc,
xmlelem,
xmlfind,
xmlfree,
xmllook,
xmlmalloc,
xmlnew,
xmlparse,
xmlprint,
xmlstrdup,
xmlvalue
\- XML parser
.SH SYNOPSIS
.de PB
.PP
.ft L
.nf
..
.PB
#include <u.h>
#include <libc.h>
#include <xml.h>
.PB
enum {
Fcrushwhite = 1,
Fstripnamespace = 2,
};
.PB
struct Xml{
Elem *root; /* root of tree */
char *doctype; /* DOCTYPE structured comment, or nil */
...
};
.PB
struct Elem {
Elem *next; /* next element at this hierarchy level */
Elem *child; /* first child of this node */
Elem *parent; /* parent of this node */
Attr *attrs; /* linked list of atributes */
char *name; /* element name */
char *pcdata; /* pcdata following this element */
int line; /* Line number (for errors) */
};
.PB
struct Attr {
Attr *next; /* next atribute */
Elem *parent; /* parent element */
char *name; /* atributes name */
char *value; /* atributes value */
};
.PB
.PD 0
.ta +\w'\fL 'u +\w'\fL 'u +6n +4n
Attr* xmlattr(Xml *xp, Attr **root, Elem *parent,
char *name, char *value)
.PB
Elem* xmlelem(Xml *xp, Elem **root, Elem *parent, char *name)
.PB
Elem* xmlfind(Xml *xp, Elem *ep, char *path)
.PB
Elem* xmllook(Elem *ep, char *path, char *attr, char *value)
.PB
Xml* xmlnew(int blksize)
.PB
Xml* xmlparse(int fd, int blksize, int flags)
.PB
char* xmlvalue(Elem *ep, char *name)
.PB
void* xmlmalloc(Xml *xp, usize size)
.PB
void* xmlcalloc(Xml *xp, usize nelem, usize elemsz)
.BP
void* xmlstrdup(Xml *xp, char *s)
.PB
void xmlfree(Xml *xp)
.PB
void xmlprint(Xml *xp, int fd)
.SH DESCRIPTION
.PP
.I Libxml
is a library for manipulating an XML document, in-memory
(known as the DOM model). Each element may have a
number of children, each of which has a number of attributes, each attribute
has a single value. All elements contain a pointer to their parent
element, the root element having a nil parent pointer.
.I Pcdata
(free form text) found between elements is attached to element which follows it.
The line numbers where each element was found is stored to allow unambigious
error messages during later analysis.
.PP
Strings are stored in two data structures: a binary tree for common names such as
element and attribute names. Uncommon names such as values and
pcdata are stored in a simple, unmanaged heap. These steps vastly reduce the memory
footprint of the parsed file and the time needed to free the XML data.
.PP
.I Xmlparse
reads the given file and builds an in-memory tree.
.I Blocksize
controls the granularity of allocation of the string heap described above,
8192 is typically used.
The
.I flags
field allows some control over the parser, it is a bitwise
.B or
of the following values:
.TP 10
.B Fcrushwhite
All strings whitespace in PCdata is replaced by a single space and leading and trailing whitespace is
removed.
.TP
.B Fstripsnamespace
Remove leading namespace strings form all element and attribute names; this effectively ignores namespaces
which can lead to parsing ambiguities, though in practice it has not been a problem—yet.
.PP
Xml trees may also be built up by calling
.I xmlnew
to create the XML tree, followed by
.I xmlelem
and
.I xmlattr
to create individual elements and attributes respectively.
.I Xmlelem
takes the address of the root of an element list to which the new
element should be appended, the address of the parent node the new
element should reference, and the name
of the node to create; It returns the address of the created element.
.PP
.I Xmlattr
attaches an attribute to an existing element. It takes a list pointer
and parent pointer like
.IR xmlelem ,
but requires both an atribute name and value,
and returns the address of the new attribute.
.PP
.I Xmllook
descends through the tree rooted at
.I ep
using the path specified in
.IR path .
It then returns if
.I elem
is nil, or continues to search for a matching element.
if
.I attr
and
.I value
are not nil, the search will continue for
for an element which contains this attribute and value pair.
.PP
.I Xmlvalue
searches the given element's attribute list and returns the
value of the attribute found or nil if that attribute is not found.
.PP
.I Xmlprint
writes the XML hierarchy rooted at \fIep\fR as text to the given
file descriptor.
.PP
.IR Xmlmalloc ,
.IR xmlcalloc ,
and
.IR xmlstrdup
allocate memory within the
.B Xml
tree.
.I Xmlfree
frees all memory used by the given
.B Xml
tree.
.SH SOURCE
/sys/src/libxml
.SH "SEE ALSO"
.IR xb (1).
.SH BUGS
Namespaces should be handled properly.
.PP
A SAX model parser will probably be needed sometime (e.g. for Ebooks).
.PP
UTF-16 headers should be respected but UTF-16 files seems rare.