From a06611f35cf39d201fb2581c81e56c7a8b7ddee6 Mon Sep 17 00:00:00 2001
From: Kartik Agaram <vc@akkartik.com>
Date: Tue, 1 Dec 2020 00:24:00 -0800
Subject: 7310 - advent day 1 part 1

In the process I had to:
* Fix a bug in reading lines from stdin into streams
* Start trailing newlines when parsing ints from streams
* Implement `find` in an array
---
 305keyboard.subx      |  6 +---
 311decimal-int.subx   | 12 ++++++++
 apps/advent2020/1a.mu | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 97 insertions(+), 5 deletions(-)
 create mode 100644 apps/advent2020/1a.mu

diff --git a/305keyboard.subx b/305keyboard.subx
index 079814fa..32159e49 100644
--- a/305keyboard.subx
+++ b/305keyboard.subx
@@ -159,13 +159,9 @@ read-line-from-real-keyboard:  # out: (addr stream byte)
     # . prologue
     55/push-ebp
     89/<- %ebp 4/r32/esp
-    # . save registers
-    50/push-eax
     #
-    (read 0 *(ebp+8))  # => eax
+    (read-line-buffered Stdin *(ebp+8))
 $read-line-from-real-keyboard:end:
-    # . restore registers
-    58/pop-to-eax
     # . epilogue
     89/<- %esp 5/r32/ebp
     5d/pop-to-ebp
diff --git a/311decimal-int.subx b/311decimal-int.subx
index 62ec51d6..badae601 100644
--- a/311decimal-int.subx
+++ b/311decimal-int.subx
@@ -60,6 +60,18 @@ parse-decimal-int-from-stream:  # in: (addr stream byte) -> result/eax: int
     # var end/edx: (addr byte) = &in->data[in->write]
     8b/-> *eax 2/r32/edx
     8d/copy-address *(eax+edx+0xc) 2/r32/edx
+    # trim a trailing newline
+    {
+      # speculatively trim
+      4a/decrement-edx
+      # if it's a newline, break
+      8a/byte-> *edx 0/r32/eax
+      81 4/subop/and %eax 0xff/imm32
+      3d/compare-eax-and 0xa/imm32/newline
+      74/jump-if-= break/disp8
+      # not a newline, so restore it
+      42/increment-edx
+    }
     #
     (parse-decimal-int-helper %ecx %edx)  # => eax
 $parse-decimal-int-from-stream:end:
diff --git a/apps/advent2020/1a.mu b/apps/advent2020/1a.mu
new file mode 100644
index 00000000..45bb5bd2
--- /dev/null
+++ b/apps/advent2020/1a.mu
@@ -0,0 +1,84 @@
+fn main -> _/ebx: int {
+  # data structure
+  var numbers-storage: (array int 0x100)  # 256 ints
+  var numbers/esi: (addr array int) <- address numbers-storage
+  var numbers-index/ecx: int <- copy 0
+  # phase 1: parse each line from stdin and add it to numbers
+  {
+    var line-storage: (stream byte 0x100)  # 256 bytes
+    var line/edx: (addr stream byte) <- address line-storage
+    {
+#?       print-string 0, "== iter\n"
+      # read line from stdin
+      clear-stream line
+      read-line-from-real-keyboard line
+      # if line is empty (not even a newline), quit
+      var done?/eax: boolean <- stream-empty? line
+      compare done?, 0  # false
+      break-if-!=
+#?       print-stream-to-real-screen line
+      # convert line to int and append it to numbers
+      var n/eax: int <- parse-decimal-int-from-stream line
+#?       print-int32-decimal 0, n
+#?       print-string 0, "\n"
+      var dest/ebx: (addr int) <- index numbers, numbers-index
+      copy-to *dest, n
+      numbers-index <- increment
+#?       print-string 0, "== "
+#?       print-int32-decimal 0, numbers-index
+#?       print-string 0, "\n"
+      loop
+    }
+  }
+  # phase 2: for each number in the array, check if 2020-it is in the rest of
+  # the array
+  var i/eax: int <- copy 0
+  {
+    compare i, numbers-index
+    break-if->=
+    var src/ebx: (addr int) <- index numbers, i
+#?     print-int32-decimal 0, *src
+#?     print-string 0, "\n"
+    var target/ecx: int <- copy 0x7e4  # 2020
+    target <- subtract *src
+    {
+      var found?/eax: boolean <- find-after numbers, i, target
+      compare found?, 0  # false
+      break-if-=
+      print-string 0, "found\n"
+      print-int32-decimal 0, *src
+      print-string 0, " "
+      print-int32-decimal 0, target
+      print-string 0, "\n"
+      target <- multiply *src
+      print-int32-decimal 0, target
+      print-string 0, "\n"
+      return 0  # success
+    }
+    i <- increment
+    loop
+  }
+  return 1  # not found
+}
+
+fn find-after _numbers: (addr array int), start: int, _target: int -> _/eax: boolean {
+  var numbers/esi: (addr array int) <- copy _numbers
+  var target/edi: int <- copy _target
+  var len/ecx: int <- length numbers
+  var i/eax: int <- copy start
+  i <- increment
+  {
+    compare i, len
+    break-if->=
+    var src/edx: (addr int) <- index numbers, i
+    # if *src == target, return true
+    compare *src, target
+    {
+      break-if-!=
+      return 1  # true
+    }
+    i <- increment
+    loop
+  }
+  return 0  # false
+}
-- 
cgit 1.4.1-2-gfad0