src/compiler/translator/HashNames.cpp

//
// Copyright 2017 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

#include "compiler/translator/HashNames.h"

#include "compiler/translator/ImmutableString.h"
#include "compiler/translator/ImmutableStringBuilder.h"
#include "compiler/translator/IntermNode.h"
#include "compiler/translator/Symbol.h"

namespace sh
{

namespace
{
constexpr const ImmutableString kHashedNamePrefix("webgl_");

ImmutableString HashName(const ImmutableString &name, ShHashFunction64 hashFunction)
{
    ASSERT(!name.empty());
    ASSERT(hashFunction);
    khronos_uint64_t number = (*hashFunction)(name.data(), name.length());

    // Build the hashed name in place.
    static const unsigned int kHexStrMaxLength = sizeof(number) * 2;
    static const size_t kHashedNameMaxLength   = kHashedNamePrefix.length() + kHexStrMaxLength;

    ImmutableStringBuilder hashedName(kHashedNameMaxLength);
    hashedName << kHashedNamePrefix;

    hashedName.appendHex(number);

    return hashedName;
}

void AddToNameMapIfNotMapped(const ImmutableString &name,
                             const ImmutableString &hashedName,
                             NameMap *nameMap)
{
    if (nameMap)
    {
        NameMap::const_iterator it = nameMap->find(name.data());
        if (it != nameMap->end())
        {
            // (How bout returning?)
            return;
        }
        (*nameMap)[name.data()] = hashedName.data();
    }
}

}  // anonymous namespace

ImmutableString HashName(const ImmutableString &name,
                         ShHashFunction64 hashFunction,
                         NameMap *nameMap)
{
    const ImmutableString kUnhashedNamePrefix(kUserDefinedNamePrefix);

    if (hashFunction == nullptr)
    {
        if (name.length() + kUnhashedNamePrefix.length() > kESSLMaxIdentifierLength)
        {
            // If the identifier length is already close to the limit, we can't prefix it. This is
            // not a problem since there are no builtins or ANGLE's internal variables that would
            // have as long names and could conflict.
            return name;
        }
        if (name == "gl_ClipDistance" || name == "gl_CullDistance" || name == "gl_LastFragData")
        {
            // NOTE(hqle): When gl_ClipDistance is re-declared, it will become an UserDefined
            // symbol. Normally, UserDefined symbols will have "_u" prefix added to their names by
            // ANGLE. However, gl_ClipDistance is an exception. If we add "_u" to its name, the
            // backend won't be able to handle it properly. So for gl_ClipDistance, we won't add
            // "_u" prefix, instead we return it original name.
            //
            // The other way is treating gl_ClipDistance as an AngleInternal symbol when a
            // re-declaration occurs. AngleInternal symbols will have their name intact. However,
            // the issue is that the current code put a lot of restrictions on AngleInternal
            // symbols. For examples:
            //  - CollectVariables.cpp will not consider AngleInternal as varying output variables.
            //  - SymbolTable.cpp will throw an exception if AngleInternal symbols are declared by
            //  users. In this case, it would be gl_ClipDistance. This is because
            //  TSymbolTable::declare() only accepts an UserDefined symbol.
            //  - And potentially many other places that have some assumptions that haven't been
            //  discovered yet.
            //
            // If re-declared gl_ClipDistance was to be an AngleInternal symbol, a special "if (name
            // == "gl_ClipDistance")" handling would have to be put into all the above mentioned
            // cases. TParseContext::declareVariable() function would also have to be modified in
            // order to assign AngleInternal symbol type to the re-declared gl_ClipDistance
            // variable.
            // Compare to only this place has to be handled if re-declared gl_ClipDistance is
            // treated as an UserDefined symbol.
            //
            // Also, gl_LastFragData should be added.
            //
            return name;
        }
        ImmutableStringBuilder prefixedName(kUnhashedNamePrefix.length() + name.length());
        prefixedName << kUnhashedNamePrefix << name;
        ImmutableString res = prefixedName;
        AddToNameMapIfNotMapped(name, res, nameMap);
        return res;
    }

    // Has a hash function
    ImmutableString hashedName = HashName(name, hashFunction);
    AddToNameMapIfNotMapped(name, hashedName, nameMap);
    return hashedName;
}

ImmutableString HashName(const TSymbol *symbol, ShHashFunction64 hashFunction, NameMap *nameMap)
{
    if (symbol->symbolType() == SymbolType::Empty)
    {
        return kEmptyImmutableString;
    }
    if (symbol->symbolType() == SymbolType::AngleInternal ||
        symbol->symbolType() == SymbolType::BuiltIn)
    {
        return symbol->name();
    }
    return HashName(symbol->name(), hashFunction, nameMap);
}

}  // namespace sh