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nga: add i/o instructions to reference implementation

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FossilOrigin-Name: f99d1a28846fc48295d49987f93717bc854e5265899d843dacb0f9b49776bb58
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crc 2018-11-21 23:32:25 +00:00
parent 2a533cd112
commit 157aba351b
1 changed files with 65 additions and 13 deletions
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78
literate/Nga.md
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@ -33,6 +33,10 @@ if the **END** instruction is run or end of memory is reached.
Endian: the image files are stored in little endian format.
I/O is not specified, but Nga does provide for adding this in a modular
manner, using three instructions to enumerate, query, and interact
with any devices provided.
## Legal
Nga derives from my earlier work on Ngaro. The following block lists
@ -60,6 +64,13 @@ Since the code is in C, we have to include some headers.
#include <string.h>
~~~
Nga uses a call table for dispatching instruction handlers. I define
a type for this here, before starting the actual code.
~~~
typedef void (*Handler)(void);
~~~
## Configuration
To make it easier to adapt Nga to a specific target, we keep some
@ -78,6 +89,7 @@ a much larger memory and stack space.
#define IMAGE_SIZE 524288 * 16
#define ADDRESSES 2048
#define STACK_DEPTH 512
#define NUM_DEVICES 0
~~~
## Numbering The Instructions
@ -86,22 +98,23 @@ For this implementation an enum is used to name each of the
instructions. For reference, here are the instructions and their
corresponding values (in decimal):
0 nop 7 jump 14 gt 21 and
1 lit <v> 8 call 15 fetch 22 or
2 dup 9 ccall 16 store 23 xor
3 drop 10 return 17 add 24 shift
4 swap 11 eq 18 sub 25 zret
5 push 12 neq 19 mul 26 end
6 pop 13 lt 20 divmod
0 nop 7 jump 14 gt 21 and 28 io query
1 lit <v> 8 call 15 fetch 22 or 29 io interact
2 dup 9 ccall 16 store 23 xor
3 drop 10 return 17 add 24 shift
4 swap 11 eq 18 sub 25 zret
5 push 12 neq 19 mul 26 end
6 pop 13 lt 20 divmod 27 io enumerate
~~~
enum vm_opcode {
VM_NOP, VM_LIT, VM_DUP, VM_DROP, VM_SWAP, VM_PUSH, VM_POP,
VM_JUMP, VM_CALL, VM_CCALL, VM_RETURN, VM_EQ, VM_NEQ, VM_LT,
VM_GT, VM_FETCH, VM_STORE, VM_ADD, VM_SUB, VM_MUL, VM_DIVMOD,
VM_AND, VM_OR, VM_XOR, VM_SHIFT, VM_ZRET, VM_END
VM_AND, VM_OR, VM_XOR, VM_SHIFT, VM_ZRET, VM_END, VM_IO_ENUM,
VM_IO_QUERY, VM_IO_INTERACT
};
#define NUM_OPS VM_END + 1
#define NUM_OPS VM_IO_INTERACT + 1
~~~
## VM State
@ -126,6 +139,13 @@ CELL address[ADDRESSES];
CELL memory[IMAGE_SIZE + 1];
~~~
For I/O devices, create the dispatch tables.
~~~
Handler IO_deviceHandlers[NUM_DEVICES + 1];
Handler IO_queryHandlers[NUM_DEVICES + 1];
~~~
## A Little More Boilerplate
Here we have a few bits of shorthand that'll be handled by the C
@ -601,6 +621,39 @@ void inst_end() {
}
~~~
**I/O ENUMERATE** pushes a value to the stack indicating the number
of provided devices.
~~~
void inst_ie() {
sp++;
TOS = NUM_DEVICES;
}
~~~
**I/O QUERY** takes a value and returns two. The top stack item
is an identifer for the type of device attached. The second indicates
a device specific version number.
~~~
void inst_iq() {
CELL Device = TOS;
inst_drop();
IO_queryHandlers[Device]();
}
~~~
**I/O INTERACT** takes a value indicating the desired device and
performs an action with the device.
~~~
void inst_ii() {
CELL Device = TOS;
inst_drop();
IO_deviceHandlers[Device]();
}
~~~
## Instruction Handler
In the past I handled the instructions via a big switch. With Nga, I
@ -611,13 +664,12 @@ So first up, the jump table itself. Just a list of pointers to the
instruction implementations, in the proper order.
~~~
typedef void (*Handler)(void);
Handler instructions[NUM_OPS] = {
inst_nop, inst_lit, inst_dup, inst_drop, inst_swap, inst_push, inst_pop,
inst_jump, inst_call, inst_ccall, inst_return, inst_eq, inst_neq, inst_lt,
inst_gt, inst_fetch, inst_store, inst_add, inst_sub, inst_mul, inst_divmod,
inst_and, inst_or, inst_xor, inst_shift, inst_zret, inst_end
inst_and, inst_or, inst_xor, inst_shift, inst_zret, inst_end, inst_ie,
inst_iq, inst_ii
};
~~~
@ -670,7 +722,7 @@ int ngaValidatePackedOpcodes(CELL opcode) {
int i;
for (i = 0; i < 4; i++) {
current = raw & 0xFF;
if (!(current >= 0 && current <= 26))
if (!(current >= 0 && current <= 29))
valid = 0;
raw = raw >> 8;
}