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| 1 | +// Copyright 2022 Google LLC |
| 2 | +// |
| 3 | +// Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | +// you may not use this file except in compliance with the License. |
| 5 | +// You may obtain a copy of the License at |
| 6 | +// |
| 7 | +// http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | +// |
| 9 | +// Unless required by applicable law or agreed to in writing, software |
| 10 | +// distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | +// See the License for the specific language governing permissions and |
| 13 | +// limitations under the License. |
| 14 | + |
| 15 | +syntax = "proto3"; |
| 16 | + |
| 17 | +package google.firestore.v1; |
| 18 | + |
| 19 | +option csharp_namespace = "Google.Cloud.Firestore.V1"; |
| 20 | +option go_package = "google.golang.org/genproto/googleapis/firestore/v1;firestore"; |
| 21 | +option java_multiple_files = true; |
| 22 | +option java_outer_classname = "BloomFilterProto"; |
| 23 | +option java_package = "com.google.firestore.v1"; |
| 24 | +option objc_class_prefix = "GCFS"; |
| 25 | +option php_namespace = "Google\\Cloud\\Firestore\\V1"; |
| 26 | +option ruby_package = "Google::Cloud::Firestore::V1"; |
| 27 | + |
| 28 | +// A sequence of bits, encoded in a byte array. |
| 29 | +// |
| 30 | +// Each byte in the `bitmap` byte array stores 8 bits of the sequence. The only |
| 31 | +// exception is the last byte, which may store 8 _or fewer_ bits. The `padding` |
| 32 | +// defines the number of bits of the last byte to be ignored as "padding". The |
| 33 | +// values of these "padding" bits are unspecified and must be ignored. |
| 34 | +// |
| 35 | +// To retrieve the first bit, bit 0, calculate: (bitmap[0] & 0x01) != 0. |
| 36 | +// To retrieve the second bit, bit 1, calculate: (bitmap[0] & 0x02) != 0. |
| 37 | +// To retrieve the third bit, bit 2, calculate: (bitmap[0] & 0x04) != 0. |
| 38 | +// To retrieve the fourth bit, bit 3, calculate: (bitmap[0] & 0x08) != 0. |
| 39 | +// To retrieve bit n, calculate: (bitmap[n / 8] & (0x01 << (n % 8))) != 0. |
| 40 | +// |
| 41 | +// The "size" of a `BitSequence` (the number of bits it contains) is calculated |
| 42 | +// by this formula: (bitmap.length * 8) - padding. |
| 43 | +message BitSequence { |
| 44 | + // The bytes that encode the bit sequence. |
| 45 | + // May have a length of zero. |
| 46 | + bytes bitmap = 1; |
| 47 | + |
| 48 | + // The number of bits of the last byte in `bitmap` to ignore as "padding". |
| 49 | + // If the length of `bitmap` is zero, then this value must be 0. |
| 50 | + // Otherwise, this value must be between 0 and 7, inclusive. |
| 51 | + int32 padding = 2; |
| 52 | +} |
| 53 | + |
| 54 | +// A bloom filter (https://en.wikipedia.org/wiki/Bloom_filter). |
| 55 | +// |
| 56 | +// The bloom filter hashes the entries with MD5 and treats the resulting 128-bit |
| 57 | +// hash as 2 distinct 64-bit hash values, interpreted as unsigned integers |
| 58 | +// using 2's complement encoding. |
| 59 | +// |
| 60 | +// These two hash values, named h1 and h2, are then used to compute the |
| 61 | +// `hash_count` hash values using the formula, starting at i=0: |
| 62 | +// |
| 63 | +// h(i) = h1 + (i * h2) |
| 64 | +// |
| 65 | +// These resulting values are then taken modulo the number of bits in the bloom |
| 66 | +// filter to get the bits of the bloom filter to test for the given entry. |
| 67 | +message BloomFilter { |
| 68 | + // The bloom filter data. |
| 69 | + BitSequence bits = 1; |
| 70 | + |
| 71 | + // The number of hashes used by the algorithm. |
| 72 | + int32 hash_count = 2; |
| 73 | +} |
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