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json_view: view_mode enum instead of bool Editable, node_kind for node::kind (#5919)

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* json_view: view_mode enum instead of bool Editable, node_kind for node::kind

basic_json_document and basic_json_view take a view_mode (read_only, the
default, or editable) instead of a bool: basic_json_document<json, true>
did not say what true means. The shortcut aliases are unchanged.

The kind of a node is a node_kind (the value_t values plus link, 10 as
before), which removes the static_cast<std::uint8_t>(value_t::...) of
every comparison. The node and image layouts are unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* json_view: node_kind in the node writers, spell out read_only, comment fixes

The builder and the edit functions take and store a node_kind instead of
casting a value_t; the numbering assertions and the comments now speak of
node_kind, and the link kind notes that it follows value_t::discarded.
The read-only aliases name view_mode::read_only like the editable ones.
view_mode.md says the mode is a compile-time property of the type.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* json_view: views of read-only documents convert to editable views

A read-only document has no edits, so a view of it reads correctly as a
view of an editable document before its first edit. The implicit
conversion lets a function taking a json_editable_view accept the views
of both modes. There is no conversion the other way: a read-only view of
an editable document would read wrong values after the next edit.

The mode comparisons in the cross-mode operator==/!= use an
is_other_mode trait, which astyle keeps compact.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann authored and GitHub committed 2026-10-26 20:13:30 +01:00
1 parent 24078c862d
commit 731f1b5bfb
38 files changed
+704 -293
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include/nlohmann/detail/view/builder.hpp
+19 -19
View File
@@ -639,11 +639,11 @@ run_found:
switch (cur())
{
case '{':
open(value_t::object);
open(node_kind::object);
++p;
goto obj_first;
case '[':
open(value_t::array);
open(node_kind::array);
++p;
goto arr_first;
default:
@@ -665,11 +665,11 @@ run_found:
if (NLOHMANN_VIEW_UNLIKELY(!string<true>())) { return false; } \
break; \
case '{': \
open(value_t::object); \
open(node_kind::object); \
++p; \
goto obj_first; \
case '[': \
open(value_t::array); \
open(node_kind::array); \
++p; \
goto arr_first; \
case '-': \
@@ -886,17 +886,17 @@ root_done:
NLOHMANN_VIEW_ALWAYS_INLINE bool literal_true()
{
return literal("true", value_t::boolean, node_flags::is_true);
return literal("true", node_kind::boolean, node_flags::is_true);
}
NLOHMANN_VIEW_ALWAYS_INLINE bool literal_false()
{
return literal("false", value_t::boolean, 0);
return literal("false", node_kind::boolean, 0);
}
NLOHMANN_VIEW_ALWAYS_INLINE bool literal_null()
{
return literal("null", value_t::null, 0);
return literal("null", node_kind::null, 0);
}
/// skip whitespace (and comments); false on a malformed comment
@@ -962,7 +962,7 @@ indent_done:
/// append a node: (kind, flags, extra, off) and the second word (len, or
/// an integer's value); two stores on little-endian targets
NLOHMANN_VIEW_ALWAYS_INLINE node* push_node(value_t k, std::uint8_t flags, std::uint16_t extra, std::size_t off, std::uint64_t second)
NLOHMANN_VIEW_ALWAYS_INLINE node* push_node(node_kind k, std::uint8_t flags, std::uint16_t extra, std::size_t off, std::uint64_t second)
{
if (NLOHMANN_VIEW_UNLIKELY(out == cap))
{
@@ -978,7 +978,7 @@ indent_done:
std::memcpy(reinterpret_cast<unsigned char*>(n), &first, 8);
std::memcpy(reinterpret_cast<unsigned char*>(n) + 8, &second, 8);
#else
n->kind = static_cast<std::uint8_t>(k);
n->kind = k;
n->flags = flags;
n->extra = extra;
n->off = static_cast<std::uint32_t>(off);
@@ -990,7 +990,7 @@ indent_done:
return n;
}
NLOHMANN_VIEW_ALWAYS_INLINE void open(value_t k)
NLOHMANN_VIEW_ALWAYS_INLINE void open(node_kind k)
{
// (base is read after push_node(), which moves the node array when it
// grows; in one expression the order of the two is unspecified)
@@ -1017,7 +1017,7 @@ indent_done:
max_depth = (std::max)(max_depth, depth);
cur_idx = idx;
cur_count = 0;
cur_is_object = k == value_t::object;
cur_is_object = k == node_kind::object;
}
NLOHMANN_VIEW_ALWAYS_INLINE void close()
@@ -1047,7 +1047,7 @@ indent_done:
/// the literal `text` at p (N counts the terminating NUL)
template<std::size_t N>
NLOHMANN_VIEW_ALWAYS_INLINE bool literal(const char (&text)[N], value_t k, std::uint8_t flags) // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays): a string literal
NLOHMANN_VIEW_ALWAYS_INLINE bool literal(const char (&text)[N], node_kind k, std::uint8_t flags) // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays): a string literal
{
const std::size_t n = N - 1;
if (NLOHMANN_VIEW_UNLIKELY(e - p < static_cast<std::ptrdiff_t>(n) || std::memcmp(p, text, n) != 0))
@@ -1126,23 +1126,23 @@ indent_done:
is_float = true;
}
value_t kind = value_t::number_float;
node_kind kind = node_kind::number_float;
if (!is_float)
{
// integers that do not fit become floats, as in parse()
if (negative)
{
kind = digits_exceed(int_start, int_digits, "9223372036854775808") ? value_t::number_float : value_t::number_integer;
kind = digits_exceed(int_start, int_digits, "9223372036854775808") ? node_kind::number_float : node_kind::number_integer;
}
else
{
kind = digits_exceed(int_start, int_digits, "18446744073709551615") ? value_t::number_float : value_t::number_unsigned;
kind = digits_exceed(int_start, int_digits, "18446744073709551615") ? node_kind::number_float : node_kind::number_unsigned;
}
}
// parse() rejects floats that overflow; only numbers whose magnitude
// could reach the largest FloatType (1e308 for double, 1e38 for
// float) need the conversion
if (NLOHMANN_VIEW_UNLIKELY(static_cast<std::int64_t>(int_digits) + exponent > std::numeric_limits<FloatType>::max_exponent10 - 8 && kind == value_t::number_float))
if (NLOHMANN_VIEW_UNLIKELY(static_cast<std::int64_t>(int_digits) + exponent > std::numeric_limits<FloatType>::max_exponent10 - 8 && kind == node_kind::number_float))
{
if (builder::float_overflows(s, p))
{
@@ -1152,7 +1152,7 @@ indent_done:
}
const auto layout = static_cast<std::uint16_t>((int_digits < 255 ? int_digits : 255) | ((frac_digits < 255 ? frac_digits : 255) << 8));
auto second = static_cast<std::uint64_t>(p - s);
if (kind != value_t::number_float)
if (kind != node_kind::number_float)
{
// integers are converted now, while their digits are in cache
const std::uint64_t m = int_digits <= 19 ? parse_upto19(int_start, static_cast<unsigned>(int_digits), e)
@@ -1175,7 +1175,7 @@ indent_done:
p = scan_string_run<Value>(p, e);
if (NLOHMANN_VIEW_LIKELY(cur() == '"'))
{
push_node(value_t::string, 0, 0, static_cast<std::size_t>(s - b), static_cast<std::uint64_t>(p - s));
push_node(node_kind::string, 0, 0, static_cast<std::size_t>(s - b), static_cast<std::uint64_t>(p - s));
++p;
return true;
}
@@ -1185,7 +1185,7 @@ indent_done:
return false;
}
p = r.p;
push_node(value_t::string, node_flags::escaped, 0, r.start, r.len);
push_node(node_kind::string, node_flags::escaped, 0, r.start, r.len);
return true;
}
};