ipc: negotiate preedit capability and caret messages

ipc.c

@@ -20,6 +20,32 @@ getlen(const unsigned char p[Ipclensz])
 	return p[0] | (p[1] << 8);
 }
 
+static void
+put32(unsigned char *p, int32_t v)
+{
+	uint32_t u;
+
+	u = v;
+	p[0] = u;
+	p[1] = u >> 8;
+	p[2] = u >> 16;
+	p[3] = u >> 24;
+}
+
+static int32_t
+get32(const unsigned char *p)
+{
+	uint32_t u;
+
+	u = (uint32_t)p[0] |
+		((uint32_t)p[1] << 8) |
+		((uint32_t)p[2] << 16) |
+		((uint32_t)p[3] << 24);
+	if(u <= INT32_MAX)
+		return u;
+	return -(int32_t)(~u) - 1;
+}
+
 int
 ipcpath(char *dst, size_t cap)
 {
@@ -82,6 +108,37 @@ ipcpackreset(unsigned char req[Ipcreqsz], int want)
 	req[0] = Ipcreqreset | (want ? Ipcreqwant : 0);
 }
 
+/* An old server sees this reserved frame as a key-zero request. */
+void
+ipcpackcap(unsigned char req[Ipcreqsz], int want)
+{
+	memset(req, 0, Ipcreqsz);
+	req[0] = Ipcext | (want ? Ipcreqwant : 0);
+	req[1] = Ipcversion;
+	req[2] = Ipcopcap;
+}
+
+int
+ipcpackcaret(unsigned char req[Ipccaretsz], int valid, int32_t x,
+	int32_t y, int32_t h)
+{
+	if(valid != 0 && valid != 1)
+		return -1;
+	if(valid && h < 0)
+		return -1;
+	memset(req, 0, Ipccaretsz);
+	req[0] = Ipcext;
+	req[1] = Ipcversion;
+	req[2] = Ipcopcaret;
+	req[3] = valid;
+	if(!valid)
+		return 0;
+	put32(req + 4, x);
+	put32(req + 8, y);
+	put32(req + 12, h);
+	return 0;
+}
+
 void
 ipcunpackreq(const unsigned char req[Ipcreqsz], int *want, uint32_t *mod,
 	uint32_t *key)
@@ -94,6 +151,52 @@ ipcunpackreq(const unsigned char req[Ipcreqsz], int *want, uint32_t *mod,
 		((uint32_t)req[5] << 24);
 }
 
+int
+ipcreqtype(const unsigned char req[Ipcreqsz])
+{
+	if((req[0] & Ipcext) == 0)
+		return Ipclegacy;
+	if(req[1] != Ipcversion)
+		return Ipcunknown;
+	switch(req[2]){
+	case Ipcopcap:
+		if((req[0] & ~(Ipcext|Ipcreqwant)) != 0 ||
+		   req[3] != 0 || req[4] != 0 || req[5] != 0)
+			return Ipcunknown;
+		return Ipccap;
+	case Ipcopcaret:
+		if(req[0] != Ipcext || req[3] > 1)
+			return Ipcunknown;
+		return Ipccaret;
+	}
+	return Ipcunknown;
+}
+
+int
+ipcunpackcaret(const unsigned char req[Ipccaretsz], int *valid,
+	int32_t *x, int32_t *y, int32_t *h)
+{
+	int32_t wireh;
+
+	if(valid == NULL || x == NULL || y == NULL || h == NULL ||
+	   ipcreqtype(req) != Ipccaret)
+		return -1;
+	wireh = get32(req + 12);
+	if(wireh < 0)
+		return -1;
+	*valid = req[3];
+	if(!*valid){
+		*x = 0;
+		*y = 0;
+		*h = 0;
+		return 0;
+	}
+	*x = get32(req + 4);
+	*y = get32(req + 8);
+	*h = wireh;
+	return 0;
+}
+
 int
 ipcreqreset(const unsigned char req[Ipcreqsz])
 {