5 files changed, 196 insertions, 2 deletions

diff --git a/src/common/include/fs.h b/src/common/include/fs.h
index 880202b..431c16f 100644
--- a/src/common/include/fs.h
+++ b/src/common/include/fs.h
@@ -8,7 +8,7 @@
 #define FT_DEV 			(0x02)
 #define FT_BLOCKDEV 	(0x04)
 #define FT_CHARDEV 		(0x08)
-#define FT_FIFO 		(0x10)
+#define FT_CHANNEL 		(0x10)		// dual-pipe
 // #define FT_SOCKET 		(0x20)		// Not yet! Semantics not defined.	 (TODO)
 
 // FM_* enum describes modes for opening a file as well as authorized operations in stat_t
diff --git a/src/common/include/token.h b/src/common/include/token.h
new file mode 100644
index 0000000..9ec1aff
--- /dev/null
+++ b/src/common/include/token.h
@@ -0,0 +1,11 @@
+#pragma once
+
+#include <stdint.h>
+#include <stddef.h>
+
+#define TOKEN_LENGTH 16
+typedef struct {
+	char bytes[TOKEN_LENGTH];
+} token_t;
+
+/* vim: set ts=4 sw=4 tw=0 noet :*/
diff --git a/src/kernel/Makefile b/src/kernel/Makefile
index 1a7c12e..f7cee23 100644
--- a/src/kernel/Makefile
+++ b/src/kernel/Makefile
@@ -3,7 +3,7 @@ OBJ = core/loader.o core/dbglog.o \
 	core/gdt.o core/idt.o core/interrupt.o core/context_switch.o core/thread.o \
 	core/frame.o core/paging.o core/freemem.o core/region.o core/kmalloc.o \
 	core/worker.o core/prng.o \
-	user/vfs.o user/nullfs.o user/process.o user/elf.o user/syscall.o \
+	user/vfs.o user/nullfs.o user/process.o user/elf.o user/syscall.o user/ipc.o \
 	dev/pci.o dev/pciide.o \
 	fs/iso9660.o
 
diff --git a/src/kernel/include/ipc.h b/src/kernel/include/ipc.h
new file mode 100644
index 0000000..5558120
--- /dev/null
+++ b/src/kernel/include/ipc.h
@@ -0,0 +1,21 @@
+#pragma once
+
+#include <token.h>
+#include <vfs.h>
+
+//  ---- Communication channels
+
+#define CHANNEL_BUFFER_SIZE 1000		// 1000 + other channel_t fields = 1024 - epsilon
+
+typedef struct {
+	fs_handle_t *a, *b;
+} fs_handle_pair_t;
+
+fs_handle_pair_t make_channel();
+
+//  ---- Tokens for sharing file descriptors between processes
+
+token_t gen_token_for(fs_handle_t *h);
+fs_handle_t *use_token(token_t tok);
+
+/* vim: set ts=4 sw=4 tw=0 noet :*/
diff --git a/src/kernel/user/ipc.c b/src/kernel/user/ipc.c
new file mode 100644
index 0000000..b23af56
--- /dev/null
+++ b/src/kernel/user/ipc.c
@@ -0,0 +1,162 @@
+#include <string.h>
+
+#include <ipc.h>
+#include <mutex.h>
+#include <thread.h>
+
+static size_t channel_read(fs_node_ptr c, size_t offset, size_t len, char* buf);
+static size_t channel_write(fs_node_ptr c, size_t offset, size_t len, const char* buf);
+static bool channel_stat(fs_node_ptr c, stat_t *st);
+static void channel_close(fs_node_ptr c);
+
+static fs_node_ops_t channel_ops = {
+	.read = channel_read,
+	.write = channel_write,
+	.close = channel_close,
+	.open = 0,
+	.readdir = 0,
+	.ioctl = 0,
+	.stat = channel_stat,
+	.walk = 0,
+	.create = 0,
+	.move = 0,
+	.delete = 0,
+	.dispose = 0,
+};
+
+typedef struct channel {
+	struct channel *other_side;
+
+	mutex_t lock;
+
+	char buf[CHANNEL_BUFFER_SIZE];
+	size_t buf_use_begin, buf_used;		// circular buffer
+} channel_t;
+
+fs_handle_pair_t make_channel() {
+	fs_handle_pair_t ret = { .a = 0, .b = 0 };
+	channel_t *a = 0, *b = 0;
+
+	a = (channel_t*)malloc(sizeof(channel_t));
+	if (a == 0) goto error;
+
+	b = (channel_t*)malloc(sizeof(channel_t));
+	if (b == 0) goto error;
+
+	ret.a = (fs_handle_t*)malloc(sizeof(fs_handle_t));
+	if (ret.a == 0) goto error;
+
+	ret.b = (fs_handle_t*)malloc(sizeof(fs_handle_t));
+	if (ret.b == 0) goto error;
+
+	a->other_side = b;
+	b->other_side = a;
+	a->lock = b->lock = MUTEX_UNLOCKED;
+	a->buf_use_begin = a->buf_used = 0;
+	b->buf_use_begin = b->buf_used = 0;
+
+	ret.a->fs = ret.b->fs = 0;
+	ret.a->node = ret.b->node = 0;
+	ret.a->ops = ret.b->ops = &channel_ops;
+	ret.a->data = a;
+	ret.b->data = b;
+	ret.a->refs = ret.b->refs = 1;
+	ret.a->mode = ret.b->mode = FM_READ | FM_WRITE;
+
+	return ret;
+
+error:
+	if (a) free(a);
+	if (b) free(b);
+	if (ret.a) free(ret.a);
+	if (ret.b) free(ret.b);
+	ret.a = ret.b = 0;
+	return ret;
+}
+
+size_t channel_read(fs_node_ptr ch, size_t offset, size_t len, char* buf) {
+	channel_t *c = (channel_t*)ch;
+	
+	mutex_lock(&c->lock);
+
+	if (c->buf_used < len) len = c->buf_used;
+
+	if (len) {
+		size_t len0 = len, len1 = 0;
+
+		if (c->buf_use_begin + len > CHANNEL_BUFFER_SIZE) {
+			len0 = CHANNEL_BUFFER_SIZE - c->buf_use_begin;
+			len1 = len - len0;
+		}
+		memcpy(buf, c->buf + c->buf_use_begin, len0);
+		if (len1) memcpy(buf + len0, c->buf, len1);
+
+		c->buf_use_begin = (c->buf_use_begin + len) % CHANNEL_BUFFER_SIZE;
+		c->buf_used -= len;
+		
+		if (c->buf_used == 0) c->buf_use_begin = 0;
+	}
+
+	mutex_unlock(&c->lock);
+
+	return len;
+}
+
+size_t channel_write(fs_node_ptr ch, size_t offset, size_t len, const char* buf) {
+	channel_t *tc = (channel_t*)ch;
+	channel_t *c = tc->other_side;
+	
+	if (c == 0) return 0;
+
+	while (!mutex_try_lock(&c->lock)) {
+		yield();
+		if (tc->other_side == 0) return 0;
+	}
+
+	if (c->buf_used + len > CHANNEL_BUFFER_SIZE) len = CHANNEL_BUFFER_SIZE - c->buf_used;
+
+	if (len) {
+		size_t len0 = len, len1 = 0;
+
+		if (c->buf_use_begin + c->buf_used + len > CHANNEL_BUFFER_SIZE) {
+			len0 = CHANNEL_BUFFER_SIZE - c->buf_use_begin - c->buf_used;
+			len1 = len - len0;
+		}
+		memcpy(c->buf + c->buf_use_begin + c->buf_used, buf, len0);
+		if (len1) memcpy(c->buf, buf + len0, len1);
+
+		c->buf_used += len;
+	}
+
+	mutex_unlock(&c->lock);
+
+	if (len) resume_on(c);	// notify processes that may be waiting for data
+
+	return len;
+}
+
+bool channel_stat(fs_node_ptr ch, stat_t *st) {
+	channel_t *c = (channel_t*)ch;
+
+	mutex_lock(&c->lock);
+
+	st->type = FT_CHANNEL;
+	st->size = c->buf_used;
+	st->access = FM_READ | FM_WRITE;
+
+	mutex_unlock(&c->lock);
+
+	return true;
+}
+
+void channel_close(fs_node_ptr ch) {
+	channel_t *c = (channel_t*)ch;
+
+	mutex_lock(&c->lock);
+
+	c->other_side->other_side = 0;
+	free(c);
+}
+
+
+/* vim: set ts=4 sw=4 tw=0 noet :*/