Add register parser and binary search for opcodes

1 files changed, 39 insertions, 0 deletions

diff --git a/newasm/parsers/decimal.s b/newasm/parsers/decimal.s
new file mode 100644
index 0000000..a1516d2
--- /dev/null
+++ b/newasm/parsers/decimal.s
@@ -0,0 +1,39 @@
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.type decimal, %function
+.global decimal
+
+// 1 not a digit
+
+// R4 input stream
+// R2 output value
+
+decimal:  LDRB    R0, [R4]    // get a char
+          CMP     R0, '0      // check if zero
+          BNE     notzero
+          ADDS    R4, 1       // consume the char
+          MOVS    R2, 0       // return value of zero
+success:  MOVS    R0, #0      // return code zero (success)
+          BX      LR
+notzero:  CMP     R0, '1      // if not [1-9] then error
+          BLO     bad
+          CMP     R0, '9
+          BHI     bad
+          ADDS    R4, 1       // consume the first digit
+          SUBS    R0, '0      // calculate the value
+          MOVS    R2, R0      // store it in R2
+loop:     LDRB    R0, [R4]    // get another char
+          CMP     R0, '0      // if not [0-9] then done
+          BLO     success
+          CMP     R0, '9
+          BHI     success
+          ADDS    R4, 1       // consume the additional digit
+          SUBS    R0, '0      // calculate the value
+          MOVS    R3, 10      // base 10
+          MULS    R2, R3      // shift result by one decimal place
+          ADDS    R2, R0      // accumulate into R2
+          B       loop        // keep getting digits
+bad:      MOVS    R0, #1      // return code 1 (not a digit)
+          BX      LR