Add support for hooking `IO#read`.

4 files changed, 27 insertions, 6 deletions

diff --git a/include/ruby/io.h b/include/ruby/io.h
index fc6240adcc..19b2036a86 100644
--- a/include/ruby/io.h
+++ b/include/ruby/io.h
@@ -59,6 +59,8 @@ PACKED_STRUCT_UNALIGNED(struct rb_io_buffer_t {
 typedef struct rb_io_buffer_t rb_io_buffer_t;
 
 typedef struct rb_io_t {
+    VALUE self;
+
     FILE *stdio_file;		/* stdio ptr for read/write if available */
     int fd;                     /* file descriptor */
     int mode;			/* mode flags: FMODE_XXXs */
diff --git a/internal/scheduler.h b/internal/scheduler.h
index be976d7be5..f5a41af064 100644
--- a/internal/scheduler.h
+++ b/internal/scheduler.h
@@ -21,7 +21,10 @@ VALUE rb_scheduler_io_wait(VALUE scheduler, VALUE io, VALUE events, VALUE timeou
 VALUE rb_scheduler_io_wait_readable(VALUE scheduler, VALUE io);
 VALUE rb_scheduler_io_wait_writable(VALUE scheduler, VALUE io);
 
-VALUE rb_scheduler_io_read(VALUE scheduler, VALUE io, VALUE buffer, VALUE offset, VALUE length);
-VALUE rb_scheduler_io_write(VALUE scheduler, VALUE io, VALUE buffer, VALUE offset, VALUE length);
+int rb_scheduler_supports_io_read(VALUE scheduler);
+VALUE rb_scheduler_io_read(VALUE scheduler, VALUE io, VALUE buffer, size_t offset, size_t length);
+
+int rb_scheduler_supports_io_write(VALUE scheduler);
+VALUE rb_scheduler_io_write(VALUE scheduler, VALUE io, VALUE buffer, size_t offset, size_t length);
 
 #endif /* RUBY_SCHEDULER_H */
diff --git a/io.c b/io.c
index fbc913bad8..f73a508a0c 100644
--- a/io.c
+++ b/io.c
@@ -2619,6 +2619,11 @@ bufread_call(VALUE arg)
 static long
 io_fread(VALUE str, long offset, long size, rb_io_t *fptr)
 {
+    VALUE scheduler = rb_thread_current_scheduler();
+    if (scheduler != Qnil && rb_scheduler_supports_io_read(scheduler)) {
+        return rb_scheduler_io_read(scheduler, fptr->self, str, offset, size);
+    }
+    
     long len;
     struct bufread_arg arg;
 
@@ -8511,6 +8516,7 @@ rb_io_initialize(int argc, VALUE *argv, VALUE io)
 	fmode |= FMODE_PREP;
     }
     MakeOpenFile(io, fp);
+    fp->self = io;
     fp->fd = fd;
     fp->mode = fmode;
     fp->encs = convconfig;
diff --git a/scheduler.c b/scheduler.c
index 4eaf12b333..9821d07636 100644
--- a/scheduler.c
+++ b/scheduler.c
@@ -59,13 +59,23 @@ VALUE rb_scheduler_io_wait_writable(VALUE scheduler, VALUE io)
     return rb_scheduler_io_wait(scheduler, io, RB_UINT2NUM(RUBY_IO_WRITABLE), Qnil);
 }
 
-VALUE rb_scheduler_io_read(VALUE scheduler, VALUE io, VALUE buffer, VALUE offset, VALUE length)
+int rb_scheduler_supports_io_read(VALUE scheduler)
 {
-    return rb_funcall(scheduler, id_io_read, 4, io, buffer, offset, length);
+    return rb_respond_to(scheduler, id_io_read);
 }
 
-VALUE rb_scheduler_io_write(VALUE scheduler, VALUE io, VALUE buffer, VALUE offset, VALUE length)
+VALUE rb_scheduler_io_read(VALUE scheduler, VALUE io, VALUE buffer, size_t offset, size_t length)
+{
+    return rb_funcall(scheduler, id_io_read, 4, io, buffer, SIZET2NUM(offset), SIZET2NUM(length));
+}
+
+int rb_scheduler_supports_io_write(VALUE scheduler)
+{
+    return rb_respond_to(scheduler, id_io_write);
+}
+
+VALUE rb_scheduler_io_write(VALUE scheduler, VALUE io, VALUE buffer, size_t offset, size_t length)
 {
     // We should ensure string has capacity to receive data, and then resize it afterwards.
-    return rb_funcall(scheduler, id_io_write, 4, io, buffer, offset, length);
+    return rb_funcall(scheduler, id_io_write, 4, io, buffer, SIZET2NUM(offset), SIZET2NUM(length));
 }