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-rw-r--r--src/libexpr/eval.cc48
-rw-r--r--src/libexpr/eval.hh3
-rw-r--r--src/libexpr/flake/flake.cc4
-rw-r--r--src/libexpr/primops.cc38
-rw-r--r--src/libexpr/primops/context.cc7
-rw-r--r--src/libexpr/primops/fetchMercurial.cc4
-rw-r--r--src/libexpr/primops/fetchTree.cc4
-rw-r--r--src/libutil/types.hh60
-rw-r--r--src/nix/eval.cc2
-rw-r--r--src/nix/repl.cc2
10 files changed, 121 insertions, 51 deletions
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index bfc5d3ebf..3332dd703 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1,5 +1,6 @@
#include "eval.hh"
#include "hash.hh"
+#include "types.hh"
#include "util.hh"
#include "store-api.hh"
#include "derivations.hh"
@@ -1694,7 +1695,7 @@ void EvalState::concatLists(Value & v, size_t nrLists, Value * * lists, const Po
void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
{
PathSet context;
- std::vector<std::string> s;
+ std::vector<BackedStringView> s;
size_t sSize = 0;
NixInt n = 0;
NixFloat nf = 0;
@@ -1705,7 +1706,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
const auto str = [&] {
std::string result;
result.reserve(sSize);
- for (const auto & part : s) result += part;
+ for (const auto & part : s) result += *part;
return result;
};
/* c_str() is not str().c_str() because we want to create a string
@@ -1715,15 +1716,18 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
char * result = allocString(sSize + 1);
char * tmp = result;
for (const auto & part : s) {
- memcpy(tmp, part.c_str(), part.size());
- tmp += part.size();
+ memcpy(tmp, part->data(), part->size());
+ tmp += part->size();
}
*tmp = 0;
return result;
};
+ Value values[es->size()];
+ Value * vTmpP = values;
+
for (auto & [i_pos, i] : *es) {
- Value vTmp;
+ Value & vTmp = *vTmpP++;
i->eval(state, env, vTmp);
/* If the first element is a path, then the result will also
@@ -1756,9 +1760,9 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
/* skip canonization of first path, which would only be not
canonized in the first place if it's coming from a ./${foo} type
path */
- s.emplace_back(
- state.coerceToString(i_pos, vTmp, context, false, firstType == nString, !first));
- sSize += s.back().size();
+ auto part = state.coerceToString(i_pos, vTmp, context, false, firstType == nString, !first);
+ sSize += part->size();
+ s.emplace_back(std::move(part));
}
first = false;
@@ -1942,34 +1946,35 @@ std::optional<string> EvalState::tryAttrsToString(const Pos & pos, Value & v,
if (i != v.attrs->end()) {
Value v1;
callFunction(*i->value, v, v1, pos);
- return coerceToString(pos, v1, context, coerceMore, copyToStore);
+ return coerceToString(pos, v1, context, coerceMore, copyToStore).toOwned();
}
return {};
}
-string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
+BackedStringView EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
bool coerceMore, bool copyToStore, bool canonicalizePath)
{
forceValue(v, pos);
- string s;
-
if (v.type() == nString) {
copyContext(v, context);
- return v.string.s;
+ return std::string_view(v.string.s);
}
if (v.type() == nPath) {
- Path path(canonicalizePath ? canonPath(v.path) : v.path);
- return copyToStore ? copyPathToStore(context, path) : path;
+ BackedStringView path(PathView(v.path));
+ if (canonicalizePath)
+ path = canonPath(*path);
+ if (copyToStore)
+ path = copyPathToStore(context, std::move(path).toOwned());
+ return path;
}
if (v.type() == nAttrs) {
auto maybeString = tryAttrsToString(pos, v, context, coerceMore, copyToStore);
- if (maybeString) {
- return *maybeString;
- }
+ if (maybeString)
+ return std::move(*maybeString);
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end()) throwTypeError(pos, "cannot coerce a set to a string");
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
@@ -1991,14 +1996,13 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
if (v.isList()) {
string result;
for (auto [n, v2] : enumerate(v.listItems())) {
- result += coerceToString(pos, *v2,
- context, coerceMore, copyToStore);
+ result += *coerceToString(pos, *v2, context, coerceMore, copyToStore);
if (n < v.listSize() - 1
/* !!! not quite correct */
&& (!v2->isList() || v2->listSize() != 0))
result += " ";
}
- return result;
+ return std::move(result);
}
}
@@ -2032,7 +2036,7 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
{
- string path = coerceToString(pos, v, context, false, false);
+ string path = coerceToString(pos, v, context, false, false).toOwned();
if (path == "" || path[0] != '/')
throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path);
return path;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 5b94a96ca..04acc5728 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -1,6 +1,7 @@
#pragma once
#include "attr-set.hh"
+#include "types.hh"
#include "value.hh"
#include "nixexpr.hh"
#include "symbol-table.hh"
@@ -251,7 +252,7 @@ public:
string. If `coerceMore' is set, also converts nulls, integers,
booleans and lists to a string. If `copyToStore' is set,
referenced paths are copied to the Nix store as a side effect. */
- string coerceToString(const Pos & pos, Value & v, PathSet & context,
+ BackedStringView coerceToString(const Pos & pos, Value & v, PathSet & context,
bool coerceMore = false, bool copyToStore = true,
bool canonicalizePath = true);
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index 809f54cc0..27ba3288b 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -253,7 +253,9 @@ static Flake getFlake(
flake.config.settings.insert({setting.name, string(state.forceStringNoCtx(*setting.value, *setting.pos))});
else if (setting.value->type() == nPath) {
PathSet emptyContext = {};
- flake.config.settings.insert({setting.name, state.coerceToString(*setting.pos, *setting.value, emptyContext, false, true, true)});
+ flake.config.settings.emplace(
+ setting.name,
+ state.coerceToString(*setting.pos, *setting.value, emptyContext, false, true, true) .toOwned());
}
else if (setting.value->type() == nInt)
flake.config.settings.insert({setting.name, state.forceInt(*setting.value, *setting.pos)});
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 0454acc3d..b07133d5e 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -350,10 +350,11 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
});
}
PathSet context;
- auto program = state.coerceToString(pos, *elems[0], context, false, false);
+ auto program = state.coerceToString(pos, *elems[0], context, false, false).toOwned();
Strings commandArgs;
- for (unsigned int i = 1; i < args[0]->listSize(); ++i)
- commandArgs.emplace_back(state.coerceToString(pos, *elems[i], context, false, false));
+ for (unsigned int i = 1; i < args[0]->listSize(); ++i) {
+ commandArgs.push_back(state.coerceToString(pos, *elems[i], context, false, false).toOwned());
+ }
try {
auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
} catch (InvalidPathError & e) {
@@ -706,7 +707,7 @@ static RegisterPrimOp primop_abort({
.fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- string s = state.coerceToString(pos, *args[0], context);
+ string s = state.coerceToString(pos, *args[0], context).toOwned();
throw Abort("evaluation aborted with the following error message: '%1%'", s);
}
});
@@ -724,7 +725,7 @@ static RegisterPrimOp primop_throw({
.fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- string s = state.coerceToString(pos, *args[0], context);
+ string s = state.coerceToString(pos, *args[0], context).toOwned();
throw ThrownError(s);
}
});
@@ -736,7 +737,7 @@ static void prim_addErrorContext(EvalState & state, const Pos & pos, Value * * a
v = *args[1];
} catch (Error & e) {
PathSet context;
- e.addTrace(std::nullopt, state.coerceToString(pos, *args[0], context));
+ e.addTrace(std::nullopt, state.coerceToString(pos, *args[0], context).toOwned());
throw;
}
}
@@ -1030,7 +1031,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
else if (i->name == state.sArgs) {
state.forceList(*i->value, pos);
for (auto elem : i->value->listItems()) {
- string s = state.coerceToString(posDrvName, *elem, context, true);
+ string s = state.coerceToString(posDrvName, *elem, context, true).toOwned();
drv.args.push_back(s);
}
}
@@ -1066,7 +1067,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
}
} else {
- auto s = state.coerceToString(*i->pos, *i->value, context, true);
+ auto s = state.coerceToString(*i->pos, *i->value, context, true).toOwned();
drv.env.emplace(key, s);
if (i->name == state.sBuilder) drv.builder = std::move(s);
else if (i->name == state.sSystem) drv.platform = std::move(s);
@@ -1399,7 +1400,7 @@ static RegisterPrimOp primop_pathExists({
static void prim_baseNameOf(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- v.mkString(baseNameOf(state.coerceToString(pos, *args[0], context, false, false)), context);
+ v.mkString(baseNameOf(*state.coerceToString(pos, *args[0], context, false, false)), context);
}
static RegisterPrimOp primop_baseNameOf({
@@ -1419,7 +1420,8 @@ static RegisterPrimOp primop_baseNameOf({
static void prim_dirOf(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- Path dir = dirOf(state.coerceToString(pos, *args[0], context, false, false));
+ auto path = state.coerceToString(pos, *args[0], context, false, false);
+ auto dir = dirOf(*path);
if (args[0]->type() == nPath) v.mkPath(dir); else v.mkString(dir, context);
}
@@ -1486,7 +1488,7 @@ static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Va
);
PathSet context;
- string path = state.coerceToString(pos, *i->value, context, false, false);
+ string path = state.coerceToString(pos, *i->value, context, false, false).toOwned();
try {
auto rewrites = state.realiseContext(context);
@@ -3288,8 +3290,8 @@ static RegisterPrimOp primop_lessThan({
static void prim_toString(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- string s = state.coerceToString(pos, *args[0], context, true, false);
- v.mkString(s, context);
+ auto s = state.coerceToString(pos, *args[0], context, true, false);
+ v.mkString(*s, context);
}
static RegisterPrimOp primop_toString({
@@ -3325,7 +3327,7 @@ static void prim_substring(EvalState & state, const Pos & pos, Value * * args, V
int start = state.forceInt(*args[0], pos);
int len = state.forceInt(*args[1], pos);
PathSet context;
- string s = state.coerceToString(pos, *args[2], context);
+ auto s = state.coerceToString(pos, *args[2], context);
if (start < 0)
throw EvalError({
@@ -3333,7 +3335,7 @@ static void prim_substring(EvalState & state, const Pos & pos, Value * * args, V
.errPos = pos
});
- v.mkString((unsigned int) start >= s.size() ? "" : string(s, start, len), context);
+ v.mkString((unsigned int) start >= s->size() ? "" : s->substr(start, len), context);
}
static RegisterPrimOp primop_substring({
@@ -3359,8 +3361,8 @@ static RegisterPrimOp primop_substring({
static void prim_stringLength(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- string s = state.coerceToString(pos, *args[0], context);
- v.mkInt(s.size());
+ auto s = state.coerceToString(pos, *args[0], context);
+ v.mkInt(s->size());
}
static RegisterPrimOp primop_stringLength({
@@ -3620,7 +3622,7 @@ static void prim_concatStringsSep(EvalState & state, const Pos & pos, Value * *
for (auto elem : args[1]->listItems()) {
if (first) first = false; else res += sep;
- res += state.coerceToString(pos, *elem, context);
+ res += *state.coerceToString(pos, *elem, context);
}
v.mkString(res, context);
diff --git a/src/libexpr/primops/context.cc b/src/libexpr/primops/context.cc
index cd7eeb588..654251c23 100644
--- a/src/libexpr/primops/context.cc
+++ b/src/libexpr/primops/context.cc
@@ -7,7 +7,8 @@ namespace nix {
static void prim_unsafeDiscardStringContext(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- v.mkString(state.coerceToString(pos, *args[0], context));
+ auto s = state.coerceToString(pos, *args[0], context);
+ v.mkString(*s);
}
static RegisterPrimOp primop_unsafeDiscardStringContext("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
@@ -32,13 +33,13 @@ static RegisterPrimOp primop_hasContext("__hasContext", 1, prim_hasContext);
static void prim_unsafeDiscardOutputDependency(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
- string s = state.coerceToString(pos, *args[0], context);
+ auto s = state.coerceToString(pos, *args[0], context);
PathSet context2;
for (auto & p : context)
context2.insert(p.at(0) == '=' ? string(p, 1) : p);
- v.mkString(s, context2);
+ v.mkString(*s, context2);
}
static RegisterPrimOp primop_unsafeDiscardOutputDependency("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
diff --git a/src/libexpr/primops/fetchMercurial.cc b/src/libexpr/primops/fetchMercurial.cc
index f808e2da5..c4e1a7bf0 100644
--- a/src/libexpr/primops/fetchMercurial.cc
+++ b/src/libexpr/primops/fetchMercurial.cc
@@ -24,7 +24,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
for (auto & attr : *args[0]->attrs) {
std::string_view n(attr.name);
if (n == "url")
- url = state.coerceToString(*attr.pos, *attr.value, context, false, false);
+ url = state.coerceToString(*attr.pos, *attr.value, context, false, false).toOwned();
else if (n == "rev") {
// Ugly: unlike fetchGit, here the "rev" attribute can
// be both a revision or a branch/tag name.
@@ -50,7 +50,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
});
} else
- url = state.coerceToString(pos, *args[0], context, false, false);
+ url = state.coerceToString(pos, *args[0], context, false, false).toOwned();
// FIXME: git externals probably can be used to bypass the URI
// whitelist. Ah well.
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 6647bd35c..d09e2d9e1 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -125,7 +125,7 @@ static void fetchTree(
if (attr.name == state.sType) continue;
state.forceValue(*attr.value, *attr.pos);
if (attr.value->type() == nPath || attr.value->type() == nString) {
- auto s = state.coerceToString(*attr.pos, *attr.value, context, false, false);
+ auto s = state.coerceToString(*attr.pos, *attr.value, context, false, false).toOwned();
attrs.emplace(attr.name,
attr.name == "url"
? type == "git"
@@ -151,7 +151,7 @@ static void fetchTree(
input = fetchers::Input::fromAttrs(std::move(attrs));
} else {
- auto url = state.coerceToString(pos, *args[0], context, false, false);
+ auto url = state.coerceToString(pos, *args[0], context, false, false).toOwned();
if (type == "git") {
fetchers::Attrs attrs;
diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index 8f72c926f..e3aca20c9 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -6,6 +6,7 @@
#include <set>
#include <string>
#include <map>
+#include <variant>
#include <vector>
namespace nix {
@@ -47,4 +48,63 @@ struct Explicit {
}
};
+
+/* This wants to be a little bit like rust's Cow type.
+ Some parts of the evaluator benefit greatly from being able to reuse
+ existing allocations for strings, but have to be able to also use
+ newly allocated storage for values.
+
+ We do not define implicit conversions, even with ref qualifiers,
+ since those can easily become ambiguous to the reader and can degrade
+ into copying behaviour we want to avoid. */
+class BackedStringView {
+private:
+ std::variant<std::string, std::string_view> data;
+
+ /* Needed to introduce a temporary since operator-> must return
+ a pointer. Without this we'd need to store the view object
+ even when we already own a string. */
+ class Ptr {
+ private:
+ std::string_view view;
+ public:
+ Ptr(std::string_view view): view(view) {}
+ const std::string_view * operator->() const { return &view; }
+ };
+
+public:
+ BackedStringView(std::string && s): data(std::move(s)) {}
+ BackedStringView(std::string_view sv): data(sv) {}
+ template<size_t N>
+ BackedStringView(const char (& lit)[N]): data(std::string_view(lit)) {}
+
+ BackedStringView(const BackedStringView &) = delete;
+ BackedStringView & operator=(const BackedStringView &) = delete;
+
+ /* We only want move operations defined since the sole purpose of
+ this type is to avoid copies. */
+ BackedStringView(BackedStringView && other) = default;
+ BackedStringView & operator=(BackedStringView && other) = default;
+
+ bool isOwned() const
+ {
+ return std::holds_alternative<std::string>(data);
+ }
+
+ std::string toOwned() &&
+ {
+ return isOwned()
+ ? std::move(std::get<std::string>(data))
+ : std::string(std::get<std::string_view>(data));
+ }
+
+ std::string_view operator*() const
+ {
+ return isOwned()
+ ? std::get<std::string>(data)
+ : std::get<std::string_view>(data);
+ }
+ Ptr operator->() const { return Ptr(**this); }
+};
+
}
diff --git a/src/nix/eval.cc b/src/nix/eval.cc
index c7517cf79..c0435461f 100644
--- a/src/nix/eval.cc
+++ b/src/nix/eval.cc
@@ -107,7 +107,7 @@ struct CmdEval : MixJSON, InstallableCommand
else if (raw) {
stopProgressBar();
- std::cout << state->coerceToString(noPos, *v, context);
+ std::cout << *state->coerceToString(noPos, *v, context);
}
else if (json) {
diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index be9f96836..2d983e98e 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -463,7 +463,7 @@ bool NixRepl::processLine(string line)
if (v.type() == nPath || v.type() == nString) {
PathSet context;
auto filename = state->coerceToString(noPos, v, context);
- pos.file = state->symbols.create(filename);
+ pos.file = state->symbols.create(*filename);
} else if (v.isLambda()) {
pos = v.lambda.fun->pos;
} else {
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-23 15:55:47 +0000