testdata/division_modulus.emb

# Copyright 2026 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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# See the License for the specific language governing permissions and
# limitations under the License.

# Test data for the `//` (flooring integer division) and `%` (flooring modulus)
# operators.

[$default byte_order: "LittleEndian"]
[(cpp) namespace: "emboss::test"]


struct ArrayOfUint16BySizeInBytes:
  0 [+1]              UInt        size_in_bytes (n)
  # (n // 2) * 2 rounds an odd byte count down to the nearest whole element.
  1 [+(n // 2) * 2]   UInt:16[]   elements


struct ChunkedPayload:
  0 [+1]                   UInt       chunk_count (n)
  # ((n + 3) // 4) * 4 rounds n up to a multiple of 4.
  1 [+((n + 3) // 4) * 4]  UInt:8[]   padded


# Virtual fields exercise constant folding through `//` and `%`, including the
# flooring sign table from the design doc.
struct Constants:
  let exact_quotient = 100 // 5
  let truncating_quotient = 100 // 7
  let negative_quotient = (0 - 7) // 2
  let exact_modulus = 100 % 5
  let truncating_modulus = 100 % 7
  let negative_modulus = (0 - 7) % 2
  let chained_div = 100 // 5 // 2
  let chained_mod = 17 % 7 % 4
  let mixed_divmod = 17 % 7 // 2


struct SignedRuntimeDivision:
  # Runtime (not constant-folded) `//` and `%` with signed dividends and both
  # constant and non-constant divisors, exercising the C++ runtime's flooring
  # adjustment, including the most negative dividend of each width.
  0  [+8]  Int   wide_dividend
  8  [+4]  Int   narrow_dividend
  12 [+1]  UInt  divisor_magnitude (d)
  let wide_quotient_by_constant = wide_dividend // 4
  let wide_remainder_by_constant = wide_dividend % 4
  # `$max(d, 1)` keeps the divisor's range clear of zero.
  let wide_quotient_by_divisor = wide_dividend // $max(d, 1)
  let wide_remainder_by_negative_divisor = wide_dividend % (0 - $max(d, 1))
  let narrow_quotient_by_negative_divisor = narrow_dividend // (0 - $max(d, 1))
  let narrow_remainder_by_negative_divisor = narrow_dividend % (0 - $max(d, 1))


# A field whose size depends on a runtime `//` with a *possibly*-zero divisor.
# When divisor == 0 the payload size -- and therefore the whole structure's
# size -- is undefined, so Ok() is false.  A nonzero divisor works normally.
struct PayloadSizedByDivision:
  0 [+1]              UInt      divisor
  1 [+16 // divisor]  UInt:8[]  payload


# A field guarded by an existence condition that involves a possibly-zero
# divisor.  This exercises the interaction with the Ok()/switch discriminant
# optimization: when divisor == 0 the condition `12 // divisor == 3` is
# undefined, so `gated`'s presence is unknown and Ok() must be false.
struct FieldGatedByDivision:
  0 [+1]  UInt  divisor
  if 12 // divisor == 3:
    1 [+1]  UInt  gated


# A virtual field whose `//` result *collapses* to a single defined value ({0})
# yet can be undefined when the divisor is zero.  Without special handling,
# codegen would fold it to a bogus literal 0; instead the accessor must return
# an Unknown result when divisor == 0.
struct CollapsingQuotient:
  0 [+1]  UInt  divisor
  let zero_or_undefined = 0 // divisor