1 files changed, 113 insertions, 0 deletions
diff --git a/filter/ahxd.c b/filter/ahxd.c
new file mode 100644
index 00000000..b557399c
--- /dev/null
+++ b/filter/ahxd.c
@@ -0,0 +1,113 @@
+#include <fitz.h>
+
+typedef struct fz_ahxd_s fz_ahxd;
+
+struct fz_ahxd_s
+{
+	fz_filter super;
+	int odd;
+	int a;
+};
+
+static inline int iswhite(int a)
+{
+	switch (a) {
+	case '\n': case '\r': case '\t': case ' ':
+	case '\0': case '\f': case '\b': case 0177:
+		return 1;
+	}
+	return 0;
+}
+
+static inline int ishex(int a)
+{
+	return (a >= 'A' && a <= 'F') ||
+		(a >= 'a' && a <= 'f') ||
+		(a >= '0' && a <= '9');
+}
+
+static inline int fromhex(int a)
+{
+	if (a >= 'A' && a <= 'F')
+		return a - 'A' + 0xA;
+	if (a >= 'a' && a <= 'f')
+		return a - 'a' + 0xA;
+	if (a >= '0' && a <= '9')
+		return a - '0';
+	return 0;
+}
+
+fz_error *
+fz_newahxd(fz_filter **fp, fz_obj *params)
+{
+	FZ_NEWFILTER(fz_ahxd, f, ahxd);
+	f->odd = 0;
+	f->a = 0;
+	return nil;
+}
+
+void
+fz_freeahxd(fz_filter *f)
+{
+	fz_free(f);
+}
+
+fz_error *
+fz_processahxd(fz_filter *filter, fz_buffer *in, fz_buffer *out)
+{
+	fz_ahxd *f = (fz_ahxd*)filter;
+	int b, c;
+
+	while (1)
+	{
+		if (in->rp == in->wp)
+			return fz_ioneedin;
+
+		if (out->wp == out->ep)
+			return fz_ioneedout;
+
+		c = *in->rp++;
+
+		if (ishex(c)) {
+			if (!f->odd) {
+				f->a = fromhex(c);
+				f->odd = 1;
+			}
+			else {
+				b = fromhex(c);
+				*out->wp++ = (f->a << 4) | b;
+				f->odd = 0;
+			}
+		}
+
+		else if (c == '>') {
+			if (f->odd)
+				*out->wp++ = (f->a << 4);
+			out->eof = 1;
+			return fz_iodone;
+		}
+
+		else if (!iswhite(c)) {
+			return fz_throw("ioerror: bad data in ahxd: '%c'", c);
+		}
+	}
+}
+
+void
+fz_pushbackahxd(fz_filter *filter, fz_buffer *in, fz_buffer *out, int n)
+{
+	int k;
+
+	assert(filter->process == fz_processahxd);
+	assert(out->wp - n >= out->rp);
+
+	k = 0;
+	while (k < n * 2) {
+		in->rp --;
+		if (ishex(*in->rp))
+			k ++;
+	}
+
+	out->wp -= n;
+}
+