kissa.bsky.social
@kissa.bsky.social
Tomfoolery, nincompoopery, programming
37 followers374 following39 posts
I guess we need negative numbers too. Maybe all numbers should be signed for now, let's deal with the unsigned/signed complexity later.
![test("read negative word", () => {
mem[0] = 0xff
mem[1] = 0xff
expect(read(0)).toBe(-1)
})
test("boundary between negative and positive", () => {
mem[0] = 0x7f
mem[1] = 0xff
mem[2] = 0x80
mem[3] = 0x00
expect(read(0)).toBe(32767)
expect(read(2)).toBe(-32768)
})](https://cdn.bsky.app/img/feed_fullsize/plain/did:plc:ih3rt6r3sesh2flndp7oefwc/bafkreid6gkdwvfiebzvan6lwsqbn23r5e3yfo4iakseml3bclxgh7brncq@jpeg)
![export function read(addr: number) {
let data
if (addr < 0 || addr >= MEM_SIZE - 1) {
if (addr === MEM_SIZE - 1) {
data = (mem[addr] << 8) + mem[0]
} else {
error(`read: invalid address ${addr}`)
}
} else {
data = (mem[addr] << 8) + mem[addr + 1]
}
if ((data & 0x8000) > 0) {
return data - 0x10000
} else {
return data
}
}](https://cdn.bsky.app/img/feed_fullsize/plain/did:plc:ih3rt6r3sesh2flndp7oefwc/bafkreicduxehp4izsptpnzg77rjjj22vaipanocinqude2qzufylptt7iq@jpeg)
kissa.bsky.social
@kissa.bsky.social
Tomfoolery, nincompoopery, programming
37 followers374 following39 posts