feat(byte_array): add get(usize) and index(usize) to ByteSpan

[giladchase]

No description provided.

[reviewable-StarkWare]

This change is 

[giladchase]

• refactor(sha256): Compute ByteArray sha256 via iterator #8540
• refactor(byte_array): delegate ByteArray iterator into ByteSpan iterator #8539
• feat(byte_array): add ByteSpan iterator #8530
• feat(byte_array): add get(usize) and index(usize) to ByteSpan #8427 👈 (View in Graphite)
• feat(ops): add get, SliceIndex and impl for ByteSpan #8417 : 1 other dependent PR (#8511 )
• feat(byte_array): add ByteSpan::to_byte_array #8416
• refactor(byte_array): extract ByteArray::append logic #8486
• feat(byte_array): add ByteArray::span and Span::len #8329
• refactor(test): remove fixed-size bytearray testutils #8343
• refactor(test): remove compare_spans util #8342
• refactor(test): remove compare_byte_array util and rework tests #8336
• main

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[TomerStarkware]

@TomerStarkware reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @orizi)

[orizi]

@orizi reviewed all commit messages.
Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @TomerStarkware)

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corelib/src/byte_array.cairo line 703 at r4 (raw file):

    fn at(self: @ByteSpan, index: usize) -> Option<u8> {
        let actual_index = index.checked_add(upcast(self.first_char_start_offset))?;
        let (word_index, index_in_word) = DivRem::div_rem(actual_index, BYTES_IN_BYTES31_NONZERO);

use bounded_int::div_rem and get index_in_word in [0,30] range.
you can use bounded_int::constrain later to decide if it is accessing the lower or upper word.

Code quote:

let (word_index, index_in_word) = DivRem::div_rem(actual_index, BYTES_IN_BYTES31_NONZERO);

---

corelib/src/byte_array.cairo line 713 at r4 (raw file):

                if word_index == self.data.len() && index_in_word < upcast(self.remainder_len) {
                    // index_in_word is from MSB, we need index from LSB.
                    let index_in_remainder = upcast(self.remainder_len) - 1 - index_in_word;

bounded_int::sub as well.

Code quote:

 let index_in_remainder = upcast(self.remainder_len) - 1 - index_in_word;

[giladchase]

Reviewable status: 4 of 5 files reviewed, 1 unresolved discussion (waiting on @orizi and @TomerStarkware)

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corelib/src/byte_array.cairo line 1014 at r9 (raw file):

Previously, orizi wrote…

should work.

Messes up semantic:

thread '<unnamed>' panicked at crates/cairo-lang-semantic/src/items/constant.rs:839:19:
Variant extract failed: `Extern(ExternFunctionId(f830))` is not of variant `GenericFunctionId::Impl`

When debugging it i switched it the +30 to -30 and it passed semantic (but failed in the logic of course), meaning probably semantic is having problems deciding what type to evaluate this to (maybe it tries to evaluate the type after the addition before taking the Div into account?).
Maybe this is a bug in semantic.

[orizi]

@orizi reviewed all commit messages.
Reviewable status: 4 of 5 files reviewed, 1 unresolved discussion (waiting on @giladchase and @TomerStarkware)

---

corelib/src/byte_array.cairo line 1014 at r9 (raw file):

Previously, giladchase wrote…

Messes up semantic:

thread '<unnamed>' panicked at crates/cairo-lang-semantic/src/items/constant.rs:839:19:
Variant extract failed: `Extern(ExternFunctionId(f830))` is not of variant `GenericFunctionId::Impl`

When debugging it i switched it the +30 to -30 and it passed semantic (but failed in the logic of course), meaning probably semantic is having problems deciding what type to evaluate this to (maybe it tries to evaluate the type after the addition before taking the Div into account?).
Maybe this is a bug in semantic.

lets go with `(Bounded::::MAX / 31 + 1).into(); instead.

[giladchase]

Reviewable status: 4 of 5 files reviewed, 1 unresolved discussion (waiting on @orizi and @TomerStarkware)

---

corelib/src/byte_array.cairo line 1014 at r9 (raw file):

Previously, orizi wrote…

lets go with `(Bounded::::MAX / 31 + 1).into(); instead.

Nice, done.

[orizi]

@orizi reviewed 1 of 1 files at r12, all commit messages.
Reviewable status: 4 of 5 files reviewed, all discussions resolved (waiting on @TomerStarkware)

[orizi]

@orizi reviewed 1 of 1 files at r11.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @giladchase)

[orizi]

@orizi reviewed 1 of 1 files at r13, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @giladchase)

[orizi]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @giladchase)

---

corelib/src/test/byte_array_test.cairo line 715 at r13 (raw file):

    assert_eq!(span[61], '#', "byte 61 - first in last_word");
    assert_eq!(span.get(62_usize), Some('$'), "byte 62 - last in last_word");
    assert_eq!(span.get(63_usize), None);

remove useless expect.

Code quote:

    assert_eq!(span.get(30_usize), Some('f'), "byte 30 - last of 1nd word");
    assert_eq!(span[31], 'g', "byte 31 - first of 2nd word");
    assert_eq!(span.get(60_usize), Some('9'), "byte 60 - last of 2nd word");
    assert_eq!(span[61], '#', "byte 61 - first in last_word");
    assert_eq!(span.get(62_usize), Some('$'), "byte 62 - last in last_word");
    assert_eq!(span.get(63_usize), None);

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[giladchase]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @orizi)

---

corelib/src/test/byte_array_test.cairo line 715 at r13 (raw file):

Previously, orizi wrote…

remove useless expect.

Done.

[orizi]

@orizi reviewed 1 of 1 files at r14, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @giladchase)

[orizi]

@orizi reviewed 2 of 2 files at r15, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @giladchase)