client__pollin diagram

client-pollin.txt

@@ -0,0 +1,50 @@
+client buffer
+
+##########++++++++A++++++A+++A++..........
+^         ^       ^      ^   ^  ^         ^
+|         |       |      |   |  |         |
+|         |       |      |   |  |         +-- end of buffer
+|         |       |      |   |  |
+|         |       |      |   |  +-- end of read(2) bytes
+|         |       |      |   |
+|         |       +-- newlines
+|         |              
+|         +-- start of line scanning
+|
++-- start of line
+
+
+# original idea
+
+- consume many lines in client__pollin
+- problem: in the echo server case, we want to write each line but a call to
+  write(2) may block, so we can't do line processing in client__pollin
+- solution: process lines in client__pollout
+
+i = scan_start
+while i < buffer_end:
+    byte = mem[i]
+    i += 1
+    if byte == '\n':
+        handle(line_start, i - line_start)
+        line_start = i
+        scan_start = i
+
+if line_start + read(2)_length >= buffer_end:
+    out_of_memory()
+    return
+
+i = line_start
+while i < line_start + read(2)_length:
+    mem[i - line_start + buffer_start] = mem[i]
+    i += 1
+
+
+# better idea
+
+in pollin handler, just read once
+indicate to the caller:
+- we read a complete line (ie 0x0a is present)
+- we read an incomplete non-empty line
+- we read nothing (EOF)
+- error from read(2)