From ee01f1a7f1e10be78bcceb4f0f42aa352a6a588f Mon Sep 17 00:00:00 2001
From: Jacques Comeaux <jacquesrcomeaux@protonmail.com>
Date: Sat, 24 Aug 2024 01:14:04 -0500
Subject: Add parsers for basic instruction types

---
 newasm/statement.s | 65 ++++++++++++++++++++++++++++++------------------------
 1 file changed, 36 insertions(+), 29 deletions(-)

(limited to 'newasm/statement.s')

diff --git a/newasm/statement.s b/newasm/statement.s
index 4a199a6..436ae03 100644
--- a/newasm/statement.s
+++ b/newasm/statement.s
@@ -5,40 +5,47 @@
 .type statement, %function
 .global statement
 
-// 1 reported an error
-
 // R4 input buffer
 // R2 output buffer
 
 statement:PUSH    {LR}
-          BL      whitespace
-          PUSH    {R2}
+          MOVS    R3, R2        // save output buffer
+          BL      whitespace    // skip leading whitespace
           BL      label
-          POP     {R2}
-          CMP     R0, #2        // check for error code 2 (no colon)
-          BNE     1f
-          ADR     R0, no_colon
-          B       err_exit
+          CMP     R0, 3         // only exit for code 3 (no colon at end of label)
+          BEQ     exit
+          MOVS    R1, R0
 1:        BL      whitespace
-          PUSH    {R2}
-          BL      opcode
-          POP     {R2}
-          BEQ     2f
-          ADR     R0, no_opcode
-          B       err_exit
-2:        LDR     R0, [R2]
+          MOVS    R2, 0         // reset output buffer
+          STRB    R2, [R3]
+          MOVS    R2, R3
+          BL      opcode        // TODO opcodes longer than 4
+          ADD     R0, R1
+          BNE     exit
+2:        MOVS    R0, R3
+          PUSH    {R3}
+          BL      putstrln
+          POP     {R3}
+          LDR     R0, [R3]
           BL      lookup
-          BEQ     3f
-          ADR     R0, not_found
-          B       err_exit
-3:        POP     {PC}          // success code already in R0
-err_exit: BL      putstrln
-          MOVS    R0, #1        // return code 1 (there was an error)
-          POP     {PC}
+          BNE     exit
+          BL      whitespace    // TODO new return code for expected whitespace
+          BNE     exit
+          ADR     R0, parsers
+          LSLS    R2, 2         // multiply by 4 to get byte offset
+          LDR     R2, [R0, R2]  // get address of parser
+          BLX     R2
+          BNE     exit
+          BL      whitespace
+          LDRB    R0, [R4]      // get a byte from the input stream
+          TST     R0, R0        // check if zero
+          BEQ     exit          // if it's zero then success
+          MOVS    R0, 0x0B      // return code 0B (extra input at end)
+exit:     POP     {PC}
 
-            .align  4
-no_colon:   .asciz  "Error: Expected colon at end of label"
-            .align  4
-no_opcode:  .asciz  "Error: Expected an opcode"
-            .align  4
-not_found:  .asciz  "Error: Opcode not found"
+          .align  4
+parsers:  .word   regreg
+          .word   regregimm
+          .word   regimm
+          .word   regregreg
+          .word   imm
-- 
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