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fix iterator invalidation issue by storing indices not iterators #54

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merged 1 commit into from
Dec 2, 2025
Merged

fix iterator invalidation issue by storing indices not iterators #54

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58 changes: 46 additions & 12 deletions include/boost/buffers/slice.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -64,9 +64,12 @@ class slice_of
using iter_type = decltype(
std::declval<BufferSequence const&>().begin());

using difference_type =
typename std::iterator_traits<iter_type>::difference_type;

BufferSequence bs_;
iter_type begin_;
iter_type end_;
difference_type begin_ = 0; // index of first buffer in sequence
difference_type end_ = 0; // 1 + index of last buffer in sequence
std::size_t len_ = 0; // length of bs_
std::size_t size_ = 0; // total bytes
std::size_t prefix_ = 0; // used prefix bytes
Expand All @@ -92,11 +95,12 @@ class slice_of
slice_of(
BufferSequence const& bs)
: bs_(bs)
, begin_(buffers::begin(bs_))
, end_(buffers::end(bs_))
{
auto it = begin_;
while(it != end_)
iter_type it = buffers::begin(bs_);
iter_type eit = buffers::end(bs_);
begin_ = 0;
end_ = std::distance(it, eit);
while(it != eit)
{
value_type b(*it);
size_ += b.size();
Expand Down Expand Up @@ -127,18 +131,39 @@ class slice_of
}

private:
iter_type
begin_iter_impl() const noexcept
{
iter_type it = buffers::begin(bs_);
std::advance(it, begin_);
return it;
}

iter_type
end_iter_impl() const noexcept
{
iter_type it = buffers::begin(bs_);
std::advance(it, end_);
return it;
}

void
remove_prefix_impl(
std::size_t n)
{
if(n > size_)
n = size_;

// nice hack to simplify the loop (M. Nejati)
n += prefix_;
size_ += prefix_;
prefix_ = 0;

iter_type it = begin_iter_impl();

while(n > 0 && begin_ != end_)
{
value_type b = *begin_;
value_type b = *it;
if(n < b.size())
{
prefix_ = n;
Expand All @@ -148,6 +173,7 @@ class slice_of
n -= b.size();
size_ -= b.size();
++begin_;
++it;
--len_;
}
}
Expand All @@ -162,12 +188,19 @@ class slice_of
return;
}
BOOST_ASSERT(begin_ != end_);

if(n > size_)
n = size_;

n += suffix_;
size_ += suffix_;
suffix_ = 0;
iter_type it = end_;
--it;
while(it != begin_)

iter_type bit = begin_iter_impl();
iter_type it = end_iter_impl();
it--;

while(it != bit)
{
value_type b = *it;
if(n < b.size())
Expand All @@ -192,6 +225,7 @@ class slice_of
}
end_ = begin_;
len_ = 0;
size_ = 0;
}

void
Expand Down Expand Up @@ -376,7 +410,7 @@ begin() const noexcept ->
const_iterator
{
return const_iterator(
this->begin_, prefix_, suffix_, 0, len_);
begin_iter_impl(), prefix_, suffix_, 0, len_);
}

template<class BufferSequence>
Expand All @@ -386,7 +420,7 @@ end() const noexcept ->
const_iterator
{
return const_iterator(
this->end_, prefix_, suffix_, len_, len_);
end_iter_impl(), prefix_, suffix_, len_, len_);
}

//------------------------------------------------
Expand Down
4 changes: 3 additions & 1 deletion test/unit/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,9 @@
# Official repository: https://github.com/cppalliance/buffers
#

add_subdirectory(../../../url/extra/test_suite test_suite)
if (NOT TARGET boost_url_test_suite)
add_subdirectory(../../../url/extra/test_suite test_suite)
endif()

file(GLOB_RECURSE PFILES CONFIGURE_DEPENDS *.cpp *.hpp)
list(APPEND PFILES
Expand Down
8 changes: 5 additions & 3 deletions test/unit/slice.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
#include <boost/static_assert.hpp>

#include <array>
#include <vector>

#include "test_buffers.hpp"
#include "test_suite.hpp"
Expand Down Expand Up @@ -119,7 +120,8 @@ struct slice_test
test::check_iterators(b, s);
}

using seq_type = std::array<const_buffer, 3>;
// Use a vector so that iterator invalidation is observable during testing.
using seq_type = std::vector<const_buffer>;

void
grind_back(
Expand Down Expand Up @@ -176,8 +178,8 @@ struct slice_test
run()
{
std::string s;
seq_type bs = make_buffers(s,
"boost.", "buffers.", "slice_" );
auto a = make_buffers(s, "boost.", "buffers.", "slice_");
seq_type bs(a.begin(), a.end());
test::check_sequence(bs, s);
//check(bs, s);
//grind(bs, s);
Expand Down
113 changes: 109 additions & 4 deletions test/unit/test_buffers.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
#include <boost/core/detail/string_view.hpp>
#include <boost/assert.hpp>
#include <boost/static_assert.hpp>

#include <string>

// Trick boostdep into requiring URL
Expand Down Expand Up @@ -255,7 +256,8 @@ template<class ConstBufferSequence>
void
grind_front(
ConstBufferSequence const& bs0,
core::string_view pat0)
core::string_view pat0,
int levels)
{
for(std::size_t n = 0; n <= pat0.size() + 1; ++n)
{
Expand All @@ -265,13 +267,37 @@ grind_front(
remove_prefix(bs, n);
check_eq(bs, pat);
check_iterators(bs, pat);

if(levels)
{
// Take a copy, blank out the original to invalidate any
// iterators, and redo the test
slice_type<ConstBufferSequence> bsc(bs);
{
slice_type<ConstBufferSequence> dummy{};
std::swap(bs, dummy);
}
grind_front(bsc, pat, levels-1);
}
}
{
auto pat = kept_front(pat0, n);
slice_type<ConstBufferSequence> bs(bs0);
keep_prefix(bs, n);
check_eq(bs, pat);
check_iterators(bs, pat);

if(levels)
{
// Take a copy, blank out the original to invalidate any
// iterators, and redo the test
slice_type<ConstBufferSequence> bsc(bs);
{
slice_type<ConstBufferSequence> dummy{};
std::swap(bs, dummy);
}
grind_front(bsc, pat, levels-1);
}
}
}
}
Expand All @@ -280,7 +306,8 @@ template<class ConstBufferSequence>
void
grind_back(
ConstBufferSequence const& bs0,
core::string_view pat0)
core::string_view pat0,
int levels)
{
for(std::size_t n = 0; n <= pat0.size() + 1; ++n)
{
Expand All @@ -290,13 +317,89 @@ grind_back(
remove_suffix(bs, n);
check_eq(bs, pat);
check_iterators(bs, pat);

if(levels)
{
// Take a copy, blank out the original to invalidate any
// iterators, and redo the test
slice_type<ConstBufferSequence> bsc(bs);
{
slice_type<ConstBufferSequence> dummy{};
std::swap(bs, dummy);
}
grind_back(bsc, pat, levels-1);
}
}
{
auto pat = kept_back(pat0, n);
slice_type<ConstBufferSequence> bs(bs0);
keep_suffix(bs, n);
check_eq(bs, pat);
check_iterators(bs, pat);

if(levels)
{
// Take a copy, blank out the original to invalidate any
// iterators, and redo the test
slice_type<ConstBufferSequence> bsc(bs);
{
slice_type<ConstBufferSequence> dummy{};
std::swap(bs, dummy);
}
grind_back(bsc, pat, levels-1);
}
}
}
}

template<class ConstBufferSequence>
void
grind_both(
ConstBufferSequence const& bs0,
core::string_view pat0,
int levels)
{
for(std::size_t n = 0; n <= pat0.size() / 2 + 2; ++n)
{
{
auto pat = trimmed_back(trimmed_front(pat0, n), n);
slice_type<ConstBufferSequence> bs(bs0);
remove_prefix(bs, n);
remove_suffix(bs, n);
check_eq(bs, pat);
check_iterators(bs, pat);

if(levels)
{
// Take a copy, blank out the original to invalidate any
// iterators, and redo the test
slice_type<ConstBufferSequence> bsc(bs);
{
slice_type<ConstBufferSequence> dummy{};
std::swap(bs, dummy);
}
grind_both(bsc, pat, levels - 1);
}
}
{
auto pat = kept_back(kept_front(pat0, n), n);
slice_type<ConstBufferSequence> bs(bs0);
keep_prefix(bs, n);
keep_suffix(bs, n);
check_eq(bs, pat);
check_iterators(bs, pat);

if(levels)
{
// Take a copy, blank out the original to invalidate any
// iterators, and redo the test
slice_type<ConstBufferSequence> bsc(bs);
{
slice_type<ConstBufferSequence> dummy{};
std::swap(bs, dummy);
}
grind_both(bsc, pat, levels - 1);
}
}
}
}
Expand All @@ -307,8 +410,9 @@ check_slice(
ConstBufferSequence const& bs,
core::string_view pat)
{
grind_front(bs, pat);
grind_back(bs, pat);
grind_front(bs, pat, 1);
grind_back(bs, pat, 1);
grind_both(bs, pat, 1);
}

// Test API and behavior of a BufferSequence
Expand All @@ -320,6 +424,7 @@ check_sequence(
BOOST_STATIC_ASSERT(is_const_buffer_sequence<T>::value);

check_iterators(t, pat);

check_slice(t, pat);
}

Expand Down
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