opengraph parser - randomcrap - random crap programs of varying quality
(HTM) git clone git://git.codemadness.org/randomcrap
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---
(DIR) commit 9991fa9ec94dff59af9449af23e91edb72ce1aa0
(DIR) parent 4a8e88fc13a3774e4f6ec098bdf23d184d7a0e69
(HTM) Author: Hiltjo Posthuma <hiltjo@codemadness.org>
Date: Sun, 28 Sep 2025 13:18:51 +0200
opengraph parser
Diffstat:
A opengraph/Makefile | 5 +++++
A opengraph/README | 5 +++++
A opengraph/main.c | 165 +++++++++++++++++++++++++++++++
A opengraph/xml.c | 456 +++++++++++++++++++++++++++++++
A opengraph/xml.h | 46 +++++++++++++++++++++++++++++++
5 files changed, 677 insertions(+), 0 deletions(-)
---
(DIR) diff --git a/opengraph/Makefile b/opengraph/Makefile
@@ -0,0 +1,5 @@
+build: clean
+ cc xml.c main.c -o main -Wall -O2
+
+clean:
+ rm -f main
(DIR) diff --git a/opengraph/README b/opengraph/README
@@ -0,0 +1,5 @@
+OpenGraph parser
+
+Parses some fields like og:title, og:description, og:image, og:video.
+
+Used by sites like Twitter, Bluesky, IMDB.
(DIR) diff --git a/opengraph/main.c b/opengraph/main.c
@@ -0,0 +1,165 @@
+#include <err.h>
+#include <stdio.h>
+#include <string.h>
+#include <strings.h>
+
+#include "xml.h"
+
+#ifdef __OpenBSD__
+#include <unistd.h>
+#else
+#define pledge(p1,p2) 0
+#endif
+
+/* ctype-like macros, but always compatible with ASCII / UTF-8 */
+#define ISCNTRL(c) ((c) < ' ' || (c) == 0x7f)
+
+#define ATTRCMP strcasecmp
+#define TAGCMP strcasecmp
+
+enum ContentType { TypeNone, TypeTitle, TypeDescription, TypeUrl, TypeImage, TypeVideo };
+static enum ContentType currenttype;
+
+static char title[4096];
+static char description[4096];
+static char image[4096];
+static char url[4096];
+static char video[4096];
+
+static char data[4096]; /* temporary buffer */
+
+static void
+printfield(const char *s)
+{
+ for (; *s; s++) {
+ if (*s == '\n')
+ putchar(' '); /* newline to space */
+ else if (ISCNTRL((unsigned char)*s))
+ continue; /* ignore control characters */
+ putchar(*s);
+ }
+}
+
+void
+xmlattr(XMLParser *x, const char *t, size_t tl, const char *a, size_t al,
+ const char *v, size_t vl)
+{
+ if (TAGCMP(t, "meta"))
+ return;
+
+ if (!ATTRCMP(a, "content")) {
+ strlcat(data, v, sizeof(data));
+ } else if (!ATTRCMP(a, "property")) {
+ if (!ATTRCMP(v, "og:title"))
+ currenttype = TypeTitle;
+ else if (!ATTRCMP(v, "og:description"))
+ currenttype = TypeDescription;
+ else if (!ATTRCMP(v, "og:url"))
+ currenttype = TypeUrl;
+ else if (!ATTRCMP(v, "og:image"))
+ currenttype = TypeImage;
+ else if (!ATTRCMP(v, "og:video"))
+ currenttype = TypeVideo;
+ else
+ currenttype = TypeNone;
+ }
+}
+
+void
+xmlattrentity(XMLParser *x, const char *t, size_t tl, const char *a, size_t al,
+ const char *v, size_t vl)
+{
+ char buf[8];
+ int len;
+
+ if (TAGCMP(t, "meta"))
+ return;
+
+ /* try to translate entity, else just pass as data to
+ * xmlattr handler. */
+ if ((len = xml_entitytostr(v, buf, sizeof(buf))) > 0)
+ xmlattr(x, t, tl, a, al, buf, (size_t)len);
+ else
+ xmlattr(x, t, tl, a, al, v, vl);
+}
+
+void
+xmltagstartparsed(XMLParser *x, const char *t, size_t tl, int isshort)
+{
+ if (strcmp(t, "meta"))
+ return;
+
+ switch (currenttype) {
+ case TypeTitle:
+ strlcpy(title, data, sizeof(title));
+ break;
+ case TypeDescription:
+ strlcpy(description, data, sizeof(description));
+ break;
+ case TypeUrl:
+ strlcpy(url, data, sizeof(url));
+ break;
+ case TypeImage:
+ strlcpy(image, data, sizeof(image));
+ break;
+ case TypeVideo:
+ strlcpy(video, data, sizeof(video));
+ break;
+ default:
+ break;
+ }
+}
+
+void
+xmltagstart(XMLParser *x, const char *t, size_t tl)
+{
+ if (strcmp(t, "meta"))
+ return;
+
+ data[0] = '\0';
+ currenttype = TypeNone;
+}
+
+int
+main(void)
+{
+ XMLParser x = { 0 };
+
+ if (pledge("stdio", NULL) == -1)
+ err(1, "pledge");
+
+ x.xmlattr = xmlattr;
+ x.xmlattrentity = xmlattrentity;
+ x.xmltagstartparsed = xmltagstartparsed;
+ x.xmltagstart = xmltagstart;
+
+ xml_parse(&x);
+
+ if (title[0]) {
+ printf("Title: ");
+ printfield(title);
+ putchar('\n');
+ }
+ if (description[0]) {
+ printf("Description: ");
+ printfield(description);
+ putchar('\n');
+ }
+ if (url[0]) {
+ printf("URL: ");
+ printfield(url);
+ putchar('\n');
+ }
+ if (image[0]) {
+ printf("Image: ");
+ printfield(image);
+ putchar('\n');
+ }
+ if (video[0]) {
+ printf("Video: ");
+ printfield(video);
+ putchar('\n');
+ }
+
+ return 0;
+}
(DIR) diff --git a/opengraph/xml.c b/opengraph/xml.c
@@ -0,0 +1,456 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "xml.h"
+
+#define ISALPHA(c) ((((unsigned)c) | 32) - 'a' < 26)
+#define ISSPACE(c) ((c) == ' ' || ((((unsigned)c) - '\t') < 5))
+
+static void
+xml_parseattrs(XMLParser *x)
+{
+ size_t namelen = 0, valuelen;
+ int c, endsep, endname = 0, valuestart = 0;
+
+ while ((c = GETNEXT()) != EOF) {
+ if (ISSPACE(c)) {
+ if (namelen)
+ endname = 1;
+ continue;
+ } else if (c == '?')
+ ; /* ignore */
+ else if (c == '=') {
+ x->name[namelen] = '\0';
+ valuestart = 1;
+ endname = 1;
+ } else if (namelen && ((endname && !valuestart && ISALPHA(c)) || (c == '>' || c == '/'))) {
+ /* attribute without value */
+ x->name[namelen] = '\0';
+ if (x->xmlattrstart)
+ x->xmlattrstart(x, x->tag, x->taglen, x->name, namelen);
+ if (x->xmlattr)
+ x->xmlattr(x, x->tag, x->taglen, x->name, namelen, "", 0);
+ if (x->xmlattrend)
+ x->xmlattrend(x, x->tag, x->taglen, x->name, namelen);
+ endname = 0;
+ x->name[0] = c;
+ namelen = 1;
+ } else if (namelen && valuestart) {
+ /* attribute with value */
+ if (x->xmlattrstart)
+ x->xmlattrstart(x, x->tag, x->taglen, x->name, namelen);
+
+ valuelen = 0;
+ if (c == '\'' || c == '"') {
+ endsep = c;
+ } else {
+ endsep = ' '; /* ISSPACE() */
+ goto startvalue;
+ }
+
+ while ((c = GETNEXT()) != EOF) {
+startvalue:
+ if (c == '&') { /* entities */
+ x->data[valuelen] = '\0';
+ /* call data function with data before entity if there is data */
+ if (valuelen && x->xmlattr)
+ x->xmlattr(x, x->tag, x->taglen, x->name, namelen, x->data, valuelen);
+ x->data[0] = c;
+ valuelen = 1;
+ while ((c = GETNEXT()) != EOF) {
+ if (c == endsep || (endsep == ' ' && (c == '>' || ISSPACE(c))))
+ break;
+ if (valuelen < sizeof(x->data) - 1)
+ x->data[valuelen++] = c;
+ else {
+ /* entity too long for buffer, handle as normal data */
+ x->data[valuelen] = '\0';
+ if (x->xmlattr)
+ x->xmlattr(x, x->tag, x->taglen, x->name, namelen, x->data, valuelen);
+ x->data[0] = c;
+ valuelen = 1;
+ break;
+ }
+ if (c == ';') {
+ x->data[valuelen] = '\0';
+ if (x->xmlattrentity)
+ x->xmlattrentity(x, x->tag, x->taglen, x->name, namelen, x->data, valuelen);
+ valuelen = 0;
+ break;
+ }
+ }
+ } else if (c != endsep && !(endsep == ' ' && (c == '>' || ISSPACE(c)))) {
+ if (valuelen < sizeof(x->data) - 1) {
+ x->data[valuelen++] = c;
+ } else {
+ x->data[valuelen] = '\0';
+ if (x->xmlattr)
+ x->xmlattr(x, x->tag, x->taglen, x->name, namelen, x->data, valuelen);
+ x->data[0] = c;
+ valuelen = 1;
+ }
+ }
+ if (c == endsep || (endsep == ' ' && (c == '>' || ISSPACE(c)))) {
+ x->data[valuelen] = '\0';
+ if (x->xmlattr)
+ x->xmlattr(x, x->tag, x->taglen, x->name, namelen, x->data, valuelen);
+ if (x->xmlattrend)
+ x->xmlattrend(x, x->tag, x->taglen, x->name, namelen);
+ break;
+ }
+ }
+ namelen = endname = valuestart = 0;
+ } else if (namelen < sizeof(x->name) - 1) {
+ x->name[namelen++] = c;
+ }
+ if (c == '>') {
+ break;
+ } else if (c == '/') {
+ x->isshorttag = 1;
+ x->name[0] = '\0';
+ namelen = 0;
+ }
+ }
+}
+
+static void
+xml_parsecomment(XMLParser *x)
+{
+ size_t datalen = 0, i = 0;
+ int c;
+
+ if (x->xmlcommentstart)
+ x->xmlcommentstart(x);
+ while ((c = GETNEXT()) != EOF) {
+ if (c == '-' || c == '>') {
+ if (x->xmlcomment && datalen) {
+ x->data[datalen] = '\0';
+ x->xmlcomment(x, x->data, datalen);
+ datalen = 0;
+ }
+ }
+
+ if (c == '-') {
+ if (++i > 2) {
+ if (x->xmlcomment)
+ for (; i > 2; i--)
+ x->xmlcomment(x, "-", 1);
+ i = 2;
+ }
+ continue;
+ } else if (c == '>' && i == 2) {
+ if (x->xmlcommentend)
+ x->xmlcommentend(x);
+ return;
+ } else if (i) {
+ if (x->xmlcomment) {
+ for (; i > 0; i--)
+ x->xmlcomment(x, "-", 1);
+ }
+ i = 0;
+ }
+
+ if (datalen < sizeof(x->data) - 1) {
+ x->data[datalen++] = c;
+ } else {
+ x->data[datalen] = '\0';
+ if (x->xmlcomment)
+ x->xmlcomment(x, x->data, datalen);
+ x->data[0] = c;
+ datalen = 1;
+ }
+ }
+}
+
+static void
+xml_parsecdata(XMLParser *x)
+{
+ size_t datalen = 0, i = 0;
+ int c;
+
+ if (x->xmlcdatastart)
+ x->xmlcdatastart(x);
+ while ((c = GETNEXT()) != EOF) {
+ if (c == ']' || c == '>') {
+ if (x->xmlcdata && datalen) {
+ x->data[datalen] = '\0';
+ x->xmlcdata(x, x->data, datalen);
+ datalen = 0;
+ }
+ }
+
+ if (c == ']') {
+ if (++i > 2) {
+ if (x->xmlcdata)
+ for (; i > 2; i--)
+ x->xmlcdata(x, "]", 1);
+ i = 2;
+ }
+ continue;
+ } else if (c == '>' && i == 2) {
+ if (x->xmlcdataend)
+ x->xmlcdataend(x);
+ return;
+ } else if (i) {
+ if (x->xmlcdata)
+ for (; i > 0; i--)
+ x->xmlcdata(x, "]", 1);
+ i = 0;
+ }
+
+ if (datalen < sizeof(x->data) - 1) {
+ x->data[datalen++] = c;
+ } else {
+ x->data[datalen] = '\0';
+ if (x->xmlcdata)
+ x->xmlcdata(x, x->data, datalen);
+ x->data[0] = c;
+ datalen = 1;
+ }
+ }
+}
+
+static int
+codepointtoutf8(long r, char *s)
+{
+ if (r == 0) {
+ return 0; /* NUL byte */
+ } else if (r <= 0x7F) {
+ /* 1 byte: 0aaaaaaa */
+ s[0] = r;
+ return 1;
+ } else if (r <= 0x07FF) {
+ /* 2 bytes: 00000aaa aabbbbbb */
+ s[0] = 0xC0 | ((r & 0x0007C0) >> 6); /* 110aaaaa */
+ s[1] = 0x80 | (r & 0x00003F); /* 10bbbbbb */
+ return 2;
+ } else if (r <= 0xFFFF) {
+ /* 3 bytes: aaaabbbb bbcccccc */
+ s[0] = 0xE0 | ((r & 0x00F000) >> 12); /* 1110aaaa */
+ s[1] = 0x80 | ((r & 0x000FC0) >> 6); /* 10bbbbbb */
+ s[2] = 0x80 | (r & 0x00003F); /* 10cccccc */
+ return 3;
+ } else {
+ /* 4 bytes: 000aaabb bbbbcccc ccdddddd */
+ s[0] = 0xF0 | ((r & 0x1C0000) >> 18); /* 11110aaa */
+ s[1] = 0x80 | ((r & 0x03F000) >> 12); /* 10bbbbbb */
+ s[2] = 0x80 | ((r & 0x000FC0) >> 6); /* 10cccccc */
+ s[3] = 0x80 | (r & 0x00003F); /* 10dddddd */
+ return 4;
+ }
+}
+
+static int
+namedentitytostr(const char *e, char *buf, size_t bufsiz)
+{
+ static const struct {
+ const char *entity;
+ int c;
+ } entities[] = {
+ { "amp;", '&' },
+ { "lt;", '<' },
+ { "gt;", '>' },
+ { "apos;", '\'' },
+ { "quot;", '"' },
+ };
+ size_t i;
+
+ /* buffer is too small */
+ if (bufsiz < 2)
+ return -1;
+
+ for (i = 0; i < sizeof(entities) / sizeof(*entities); i++) {
+ if (!strcmp(e, entities[i].entity)) {
+ buf[0] = entities[i].c;
+ buf[1] = '\0';
+ return 1;
+ }
+ }
+ return -1;
+}
+
+static int
+numericentitytostr(const char *e, char *buf, size_t bufsiz)
+{
+ long l;
+ int len;
+ char *end;
+
+ /* buffer is too small */
+ if (bufsiz < 5)
+ return -1;
+
+ errno = 0;
+ /* hex (16) or decimal (10) */
+ if (*e == 'x')
+ l = strtol(++e, &end, 16);
+ else
+ l = strtol(e, &end, 10);
+ /* invalid value or not a well-formed entity or invalid code point */
+ if (errno || e == end || *end != ';' || l < 0 || l > 0x10ffff ||
+ (l >= 0xd800 && l <= 0xdfff))
+ return -1;
+ len = codepointtoutf8(l, buf);
+ buf[len] = '\0';
+
+ return len;
+}
+
+/* convert named- or numeric entity string to buffer string
+ * returns byte-length of string or -1 on failure. */
+int
+xml_entitytostr(const char *e, char *buf, size_t bufsiz)
+{
+ /* doesn't start with & */
+ if (e[0] != '&')
+ return -1;
+ /* numeric entity */
+ if (e[1] == '#')
+ return numericentitytostr(e + 2, buf, bufsiz);
+ else /* named entity */
+ return namedentitytostr(e + 1, buf, bufsiz);
+}
+
+void
+xml_parse(XMLParser *x)
+{
+ size_t datalen, tagdatalen;
+ int c, isend;
+
+ while ((c = GETNEXT()) != EOF && c != '<')
+ ; /* skip until < */
+
+ while (c != EOF) {
+ if (c == '<') { /* parse tag */
+ if ((c = GETNEXT()) == EOF)
+ return;
+
+ if (c == '!') { /* CDATA and comments */
+ for (tagdatalen = 0; (c = GETNEXT()) != EOF;) {
+ /* NOTE: sizeof(x->data) must be at least sizeof("[CDATA[") */
+ if (tagdatalen <= sizeof("[CDATA[") - 1)
+ x->data[tagdatalen++] = c;
+ if (c == '>')
+ break;
+ else if (c == '-' && tagdatalen == sizeof("--") - 1 &&
+ (x->data[0] == '-')) {
+ xml_parsecomment(x);
+ break;
+ } else if (c == '[') {
+ if (tagdatalen == sizeof("[CDATA[") - 1 &&
+ !strncmp(x->data, "[CDATA[", tagdatalen)) {
+ xml_parsecdata(x);
+ break;
+ }
+ }
+ }
+ } else {
+ /* normal tag (open, short open, close), processing instruction. */
+ x->tag[0] = c;
+ x->taglen = 1;
+ x->isshorttag = isend = 0;
+
+ /* treat processing instruction as short tag, don't strip "?" prefix. */
+ if (c == '?') {
+ x->isshorttag = 1;
+ } else if (c == '/') {
+ if ((c = GETNEXT()) == EOF)
+ return;
+ x->tag[0] = c;
+ isend = 1;
+ }
+
+ while ((c = GETNEXT()) != EOF) {
+ if (c == '/')
+ x->isshorttag = 1; /* short tag */
+ else if (c == '>' || ISSPACE(c)) {
+ x->tag[x->taglen] = '\0';
+ if (isend) { /* end tag, starts with </ */
+ while (c != '>' && c != EOF) /* skip until > */
+ c = GETNEXT();
+ if (x->xmltagend)
+ x->xmltagend(x, x->tag, x->taglen, x->isshorttag);
+ x->tag[0] = '\0';
+ x->taglen = 0;
+ } else {
+ /* start tag */
+ if (x->xmltagstart)
+ x->xmltagstart(x, x->tag, x->taglen);
+ if (ISSPACE(c))
+ xml_parseattrs(x);
+ if (x->xmltagstartparsed)
+ x->xmltagstartparsed(x, x->tag, x->taglen, x->isshorttag);
+ }
+ /* call tagend for short tag or processing instruction */
+ if (x->isshorttag) {
+ if (x->xmltagend)
+ x->xmltagend(x, x->tag, x->taglen, x->isshorttag);
+ x->tag[0] = '\0';
+ x->taglen = 0;
+ }
+ break;
+ } else if (x->taglen < sizeof(x->tag) - 1)
+ x->tag[x->taglen++] = c; /* NOTE: tag name truncation */
+ }
+ }
+ } else {
+ /* parse tag data */
+ datalen = 0;
+ if (x->xmldatastart)
+ x->xmldatastart(x);
+ while ((c = GETNEXT()) != EOF) {
+ if (c == '&') {
+ if (datalen) {
+ x->data[datalen] = '\0';
+ if (x->xmldata)
+ x->xmldata(x, x->data, datalen);
+ }
+ x->data[0] = c;
+ datalen = 1;
+ while ((c = GETNEXT()) != EOF) {
+ if (c == '<')
+ break;
+ if (datalen < sizeof(x->data) - 1)
+ x->data[datalen++] = c;
+ else {
+ /* entity too long for buffer, handle as normal data */
+ x->data[datalen] = '\0';
+ if (x->xmldata)
+ x->xmldata(x, x->data, datalen);
+ x->data[0] = c;
+ datalen = 1;
+ break;
+ }
+ if (c == ';') {
+ x->data[datalen] = '\0';
+ if (x->xmldataentity)
+ x->xmldataentity(x, x->data, datalen);
+ datalen = 0;
+ break;
+ }
+ }
+ } else if (c != '<') {
+ if (datalen < sizeof(x->data) - 1) {
+ x->data[datalen++] = c;
+ } else {
+ x->data[datalen] = '\0';
+ if (x->xmldata)
+ x->xmldata(x, x->data, datalen);
+ x->data[0] = c;
+ datalen = 1;
+ }
+ }
+ if (c == '<') {
+ x->data[datalen] = '\0';
+ if (x->xmldata && datalen)
+ x->xmldata(x, x->data, datalen);
+ if (x->xmldataend)
+ x->xmldataend(x);
+ break;
+ }
+ }
+ }
+ }
+}
(DIR) diff --git a/opengraph/xml.h b/opengraph/xml.h
@@ -0,0 +1,46 @@
+#ifndef XML_H
+#define XML_H
+
+#include <stdio.h>
+
+typedef struct xmlparser {
+ /* handlers */
+ void (*xmlattr)(struct xmlparser *, const char *, size_t,
+ const char *, size_t, const char *, size_t);
+ void (*xmlattrend)(struct xmlparser *, const char *, size_t,
+ const char *, size_t);
+ void (*xmlattrstart)(struct xmlparser *, const char *, size_t,
+ const char *, size_t);
+ void (*xmlattrentity)(struct xmlparser *, const char *, size_t,
+ const char *, size_t, const char *, size_t);
+ void (*xmlcdatastart)(struct xmlparser *);
+ void (*xmlcdata)(struct xmlparser *, const char *, size_t);
+ void (*xmlcdataend)(struct xmlparser *);
+ void (*xmlcommentstart)(struct xmlparser *);
+ void (*xmlcomment)(struct xmlparser *, const char *, size_t);
+ void (*xmlcommentend)(struct xmlparser *);
+ void (*xmldata)(struct xmlparser *, const char *, size_t);
+ void (*xmldataend)(struct xmlparser *);
+ void (*xmldataentity)(struct xmlparser *, const char *, size_t);
+ void (*xmldatastart)(struct xmlparser *);
+ void (*xmltagend)(struct xmlparser *, const char *, size_t, int);
+ void (*xmltagstart)(struct xmlparser *, const char *, size_t);
+ void (*xmltagstartparsed)(struct xmlparser *, const char *,
+ size_t, int);
+
+#define GETNEXT getchar_unlocked
+
+ /* current tag */
+ char tag[1024];
+ size_t taglen;
+ /* current tag is a short tag ? <tag /> */
+ int isshorttag;
+ /* current attribute name */
+ char name[1024];
+ /* data buffer used for tag data, CDATA and attribute data */
+ char data[BUFSIZ];
+} XMLParser;
+
+int xml_entitytostr(const char *, char *, size_t);
+void xml_parse(XMLParser *);
+#endif