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Delay dictionary realization when it's enumerated #34

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Nov 16, 2020
Merged

Delay dictionary realization when it's enumerated #34

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47 changes: 40 additions & 7 deletions Bencodex/Types/Dictionary.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -38,20 +38,20 @@ public Dictionary(IEnumerable<KeyValuePair<IKey, IValue>> value)

public static Dictionary Empty => default;

public int Count => Value?.Count ?? 0;
public int Count => Value.Count;

public IEnumerable<IKey> Keys =>
Value?.Keys ?? Enumerable.Empty<IKey>();
Value.Keys;

public IEnumerable<IValue> Values =>
Value?.Values ?? Enumerable.Empty<IValue>();
Value.Values;

[Pure]
public string Inspection
{
get
{
if (Value is null || !this.Any())
if (_value is null || !Value.Any())
{
return "{}";
}
Expand Down Expand Up @@ -297,12 +297,16 @@ IImmutableDictionary<IKey, IValue> other
[Pure]
public IEnumerable<byte[]> EncodeIntoChunks()
{
// FIXME: avoid duplication between this and EncodeToStream()
yield return _dictionaryPrefix;

if (!(Value is null))
if (!(_value is null))
{
var @enum = _value.Dict
?? _value.Pairs
?? Enumerable.Empty<KeyValuePair<IKey, IValue>>();
IEnumerable<ValueTuple<byte?, byte[], IValue>> rawPairs =
from pair in this
from pair in @enum
select (
pair.Key.KeyPrefix,
pair.Key.EncodeAsByteArray(),
Expand All @@ -312,8 +316,19 @@ from pair in this
triple => (triple.Item1, triple.Item2),
keyPairComparer
);
var byteArrayComparer = default(ByteArrayComparer);
(byte? keyPrefix, byte[] key)? prev = null;
foreach ((byte? keyPrefix, byte[] key, IValue value) in orderedPairs)
{
// Skip duplicates
if (_value.Dict is null && prev is { } p)
{
if (p.keyPrefix == keyPrefix && byteArrayComparer.Compare(p.key, key) == 0)
{
continue;
}
}

if (keyPrefix != null)
{
yield return _unicodeKeyPrefix;
Expand All @@ -328,6 +343,8 @@ from pair in this
{
yield return chunk;
}

prev = (keyPrefix, key);
}
}

Expand All @@ -336,12 +353,16 @@ from pair in this

public void EncodeToStream(Stream stream)
{
// FIXME: avoid duplication between this and EncodeIntoChunks()
stream.WriteByte(_dictionaryPrefix[0]);

if (!(_value is null))
{
var @enum = _value.Dict
?? _value.Pairs
?? Enumerable.Empty<KeyValuePair<IKey, IValue>>();
IEnumerable<ValueTuple<byte?, byte[], IValue>> rawPairs =
from pair in this
from pair in @enum
select (
pair.Key.KeyPrefix,
pair.Key.EncodeAsByteArray(),
Expand All @@ -351,8 +372,19 @@ from pair in this
triple => (triple.Item1, triple.Item2),
keyPairComparer
);
var byteArrayComparer = default(ByteArrayComparer);
(byte? keyPrefix, byte[] key)? prev = null;
foreach ((byte? keyPrefix, byte[] key, IValue value) in orderedPairs)
{
// Skip duplicates
if (_value.Dict is null && prev is { } p)
{
if (p.keyPrefix == keyPrefix && byteArrayComparer.Compare(p.key, key) == 0)
{
continue;
}
}

if (keyPrefix != null)
{
stream.WriteByte(_unicodeKeyPrefix[0]);
Expand All @@ -365,6 +397,7 @@ from pair in this
stream.WriteByte(CommonVariables.Separator[0]);
stream.Write(key, 0, key.Length);
value.EncodeToStream(stream);
prev = (keyPrefix, key);
}
}

Expand Down
3 changes: 2 additions & 1 deletion CHANGES.md
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ To be released.
- `Bencodex.Types.Dictionary` became not to immediately realize the inner
hash table, but do it when it needs (e.g., when to look up a key) instead.
Note that this change does not cause any API changes, but just purposes
faster instantiation. [[#33]]
faster instantiation. [[#33], [#34]]

[#7]: https://github.com/planetarium/bencodex.net/pull/7
[#11]: https://github.com/planetarium/bencodex.net/pull/11
Expand All @@ -120,6 +120,7 @@ To be released.
[#28]: https://github.com/planetarium/bencodex.net/pull/28
[#32]: https://github.com/planetarium/bencodex.net/pull/32
[#33]: https://github.com/planetarium/bencodex.net/pull/33
[#34]: https://github.com/planetarium/bencodex.net/pull/34
[nullable reference types]: https://docs.microsoft.com/en-us/dotnet/csharp/nullable-references
[RTL]: https://en.wikipedia.org/wiki/Right-to-left
[FNV]: https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
Expand Down