first version of arm32 unpacker: 240 bytes

asm_unpackers/unpack_arm32.S

@@ -0,0 +1,106 @@
+.arm
+
+.section .text
+
+.global upkr_unpack
+.type upkr_unpack, %function
+// r0 .. out_ptr (returned)
+// r1 .. in_ptr (returned)
+// r2 .. state
+// r3 .. offset
+// r4 .. prev_was_literal / decode_length ret
+// r5 .. context index
+// r6 .. decode_length temp
+// r7 .. probs ptr
+// r8-r11 .. decode_bit temp
+// r12 .. decode_length return address
+upkr_unpack:
+    push { r3-r11, lr }
+
+	mov r2, #384
+    movs r3, #128
+.Lclear:
+    subs r2, r2, #1
+    strb r3, [sp, -r2]
+    bne .Lclear
+
+.Lloop:
+    movs r5, #0
+    bl upkr_decode_bit
+    bcc .Ldata
+.Lmatch:
+	mov r5, #256
+    cmp r4, #0
+    beq 1f
+
+    bl upkr_decode_bit
+    bcc 2f
+
+1:
+    bl upkr_decode_length
+    subs r3, r4, #1
+    popeq { r3-r11, pc }
+2:
+
+	mov r5, #256+64
+    bl upkr_decode_length
+.Lcopy_loop:
+    ldrb r5, [r0, -r3]
+.Lstore:
+    strb r5, [r0], #1
+    subs r4, r4, #1
+    bgt .Lcopy_loop
+    b .Lloop
+
+.Ldata:
+    movs r5, #1
+
+.Ldata_loop:
+    bl upkr_decode_bit
+    adcs r5, r5, r5
+	rsbs r4, r5, #256
+    bgt .Ldata_loop
+	b .Lstore
+
+.type upkr_decode_length, %function
+upkr_decode_length:
+	mov r12, lr
+
+    movs r6, #0
+	mov r4, #1
+.Lbit_loop:
+    adds r5, r5, #1
+    bl upkr_decode_bit
+	addcc r4, r4, r6
+	movcc pc, r12
+
+    adds r5, r5, #1
+    bl upkr_decode_bit
+    addcs r6, r6, r4
+    lsls r4, r4, #1
+    b .Lbit_loop
+
+.type upkr_decode_bit, %function
+upkr_fill_state:
+    ldrb r8, [r1], #1
+	orr r2, r8, r2, lsl #8
+
+upkr_decode_bit:
+	cmp r2, #4096
+	blt upkr_fill_state
+
+    ldrb r8, [sp, -r5]
+	and r9, r2, #255
+	add r9, r9, #1
+	cmp r8, r9
+	rsbcs r8, r8, #256
+	mov r9, r2, lsr#8
+	addcc r9, r9, #1
+	mul r9, r8, r9
+	sub r2, r2, r9
+	add r9, r8, #8
+	sub r8, r8, r9, lsr#4
+	rsbcs r8, r8, #256
+	strb r8, [sp, -r5]
+	mov pc, r14
+