Add capn_(inflate|deflate) for converting to/from the packed form

Makefile

@@ -8,5 +8,5 @@ clean:
 %.o: %.c *.h *.inc
 	$(CC) -Wall -Werror -g -O2 -c $< -o $@
 
-capn.so: capn-malloc.o capn.o
+capn.so: capn-malloc.o capn-stream.o capn.o
 	$(CC) -shared -Wall -Werror -fPIC -g -O2 $^ -o $@

capn-stream.c

@@ -0,0 +1,187 @@
+/* vim: set sw=8 ts=8 sts=8 noet: */
+#include "capn.h"
+#include <string.h>
+
+#ifndef min
+static int min(int a, int b) { return (a < b) ? a : b; }
+#endif
+
+int capn_deflate(struct capn_stream* s) {
+	while (s->avail_in) {
+		int i, sz = 0;
+		uint8_t hdr = 0;
+		uint8_t *p;
+
+		if (!s->avail_out)
+			return CAPN_NEED_MORE_OUT;
+
+		if (s->raw > 0) {
+			sz = min(s->raw, min(s->avail_in, s->avail_out));
+			memcpy(s->next_out, s->next_in, sz);
+			s->next_out += sz;
+			s->next_in += sz;
+			s->avail_out -= sz;
+			s->avail_in -= sz;
+			s->raw -= sz;
+			continue;
+		}
+
+		if (s->avail_in < 8)
+			return CAPN_NEED_MORE_IN;
+
+		for (i = 0; i < 8; i++) {
+			if (s->next_in[i]) {
+				sz ++;
+				hdr |= 1 << i;
+			}
+		}
+
+		switch (sz) {
+		case 0:
+			if (s->avail_out < 2)
+				return CAPN_NEED_MORE_OUT;
+
+			s->next_out[0] = hdr;
+			for (sz = 1; sz < min(s->avail_in/8, 256); sz++) {
+				if (((uint64_t*) s->next_in)[sz] != 0) {
+					break;
+				}
+			}
+
+			s->next_out[1] = (uint8_t) (sz-1);
+			s->next_in += sz*8;
+			s->avail_in -= sz*8;
+			s->next_out += 2;
+			s->avail_out -= 2;
+			continue;
+
+		case 8:
+			if (s->avail_out < 10)
+				return CAPN_NEED_MORE_OUT;
+
+			s->next_out[0] = hdr;
+			memcpy(s->next_out+1, s->next_in, 8);
+			s->next_in += 8;
+			s->avail_in -= 8;
+
+			s->raw = min(s->avail_in, 256*8);
+			if ((p = memchr(s->next_in, 0, s->raw)) != NULL) {
+				s->raw = (p - s->next_in) & ~7;
+			}
+
+			s->next_out[9] = (uint8_t) (s->raw/8);
+			s->next_out += 10;
+			s->avail_out -= 10;
+			continue;
+
+		default:
+			if (s->avail_out < 1 + sz)
+				return CAPN_NEED_MORE_OUT;
+
+			*(s->next_out++) = hdr;
+			for (i = 0; i < 8; i++) {
+				if (s->next_in[i]) {
+					*(s->next_out++) = s->next_in[i];
+				}
+			}
+			s->avail_out -= sz + 1;
+			s->next_in += 8;
+			s->avail_in -= 8;
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+int capn_inflate(struct capn_stream* s) {
+	for (;;) {
+		int i, sz;
+		uint8_t hdr;
+
+		if (s->zeros > 0) {
+			if (s->avail_out == 0)
+				return CAPN_NEED_MORE_OUT;
+
+			sz = min(s->avail_out, s->zeros);
+			memset(s->next_out, 0, sz);
+			s->next_out += sz;
+			s->avail_out -= sz;
+			s->zeros -= sz;
+			continue;
+		}
+
+		if (s->raw > 0) {
+			if (s->avail_in == 0)
+				return CAPN_NEED_MORE_IN;
+			else if (s->avail_out == 0)
+				return CAPN_NEED_MORE_OUT;
+
+			sz = min(min(s->avail_out, s->raw), s->avail_in);
+			memcpy(s->next_out, s->next_in, sz);
+			s->next_in += sz;
+			s->next_out += sz;
+			s->avail_in -= sz;
+			s->avail_out -= sz;
+			s->raw -= sz;
+			continue;
+		}
+
+		if (s->avail_in == 0)
+			return 0;
+		else if (s->avail_out < 8)
+			return CAPN_NEED_MORE_OUT;
+		else if (s->avail_in < 2)
+			return CAPN_NEED_MORE_IN;
+
+		switch (s->next_in[0]) {
+		case 0xFF:
+			/* 0xFF is followed by 8 bytes raw, followed by
+			 * a byte with length in words to read raw */
+			if (s->avail_in < 10)
+				return CAPN_NEED_MORE_IN;
+
+			memcpy(s->next_out, s->next_in+1, 8);
+			s->raw = (int) s->next_in[9] * 8;
+			s->next_in += 10;
+			s->avail_in -= 10;
+			s->next_out += 8;
+			s->avail_out -= 8;
+			continue;
+
+		case 0x00:
+			/* 0x00 is followed by a single byte indicating
+			 * the count of consecutive zero value words
+			 * minus 1 */
+			s->zeros = (int) (s->next_in[1] + 1) * 8;
+			s->next_in += 2;
+			s->avail_in -= 2;
+			continue;
+
+		default:
+			sz = 0;
+			hdr = s->next_in[1];
+			for (i = 0; i < 8; i++) {
+				if (hdr & (1 << i))
+					sz++;
+			}
+			if (s->avail_in < 2 + sz)
+				return CAPN_NEED_MORE_IN;
+
+			s->next_in += 2;
+
+			for (i = 0; i < 8; i++) {
+				if (hdr & (1 << i)) {
+					*(s->next_out++) = *(s->next_in++);
+				} else {
+					*(s->next_out++) = 0;
+				}
+			}
+
+			s->avail_out -= 8;
+			s->avail_in -= 2 + sz;
+			continue;
+		}
+	}
+}
+

capn.h

@@ -212,6 +212,33 @@ CAPN_INLINE int capn_set64(struct capn_ptr *p, int off, uint64_t val);
 void capn_init_malloc(struct capn *c);
 void capn_free_all(struct capn *c);
 
+/* capn_stream encapsulates the needed fields for capn_(deflate|inflate) in a
+ * similar manner to z_stream from zlib
+ *
+ * The user should set next_in, avail_in, next_out, avail_out to the
+ * available in/out buffers before calling capn_(deflate|inflate).
+ *
+ * Other fields should be zero initialized.
+ */
+struct capn_stream {
+	uint8_t *next_in;
+	int avail_in;
+	uint8_t *next_out;
+	int avail_out;
+	int zeros, raw;
+};
+
+#define CAPN_NEED_MORE_IN -1
+#define CAPN_NEED_MORE_OUT -2
+
+/* capn_deflate deflates a stream to the packed format
+ * capn_inflate inflates a stream from the packed format
+ *
+ * They will return CAPN_NEED_MORE_(IN|OUT) as appropriate or 0 if the entire
+ * input has been processed.
+ */
+int capn_deflate(struct capn_stream*);
+int capn_inflate(struct capn_stream*);
 
 int capn_marshal_iptr(const union capn_iptr*, struct capn_ptr*, int off);