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ifcviewer: drop unused SidecarHeader reserved field, bump v8 -> v9

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The reserved uint32_t was always written as 0 and never inspected on
read.  Removing it shrinks the header from 16 to 12 bytes; the version
bump makes pre-existing sidecars fail the version check cleanly rather
than misreading by 4 bytes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
Dion Moult
2026-04-28 19:40:00 +10:00
parent 8282f691e8
commit 633c613da2
3 changed files with 8 additions and 8 deletions
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src/ifcviewer/README.md
+3 -3
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@@ -116,7 +116,7 @@ engine with a Qt6 interface and OpenGL 4.5 rendering.
| `InstancedGeometry.h` | Shared structs: `MeshInfo`, `InstanceCpu`, `InstanceGpu`, chunk records | | `InstancedGeometry.h` | Shared structs: `MeshInfo`, `InstanceCpu`, `InstanceGpu`, chunk records |
| `BvhAccel.h/cpp` | Median-split BVH builder; operates on instance world-AABBs | | `BvhAccel.h/cpp` | Median-split BVH builder; operates on instance world-AABBs |
| `LodBuilder.h/cpp` | Post-stream decimation of unique meshes via meshoptimizer (`simplifySloppy`) | | `LodBuilder.h/cpp` | Post-stream decimation of unique meshes via meshoptimizer (`simplifySloppy`) |
| `SidecarCache.h/cpp` | Raw binary `.ifcview` (v8) sidecar read/write | | `SidecarCache.h/cpp` | Raw binary `.ifcview` (v9) sidecar read/write |
| `AppSettings.h/cpp` | Persisted preferences (geometry library, stats overlay, backface culling) | | `AppSettings.h/cpp` | Persisted preferences (geometry library, stats overlay, backface culling) |
| `SettingsWindow.h/cpp` | Settings dialog | | `SettingsWindow.h/cpp` | Settings dialog |
| `CMakeLists.txt` | Build configuration | | `CMakeLists.txt` | Build configuration |
@@ -293,13 +293,13 @@ while stack not empty:
Depth 64 is enough for billions of items on any balanced tree. The stack Depth 64 is enough for billions of items on any balanced tree. The stack
is on the C++ stack, zero per-frame allocation. is on the C++ stack, zero per-frame allocation.
#### Sidecar format (`.ifcview`, v8) #### Sidecar format (`.ifcview`, v9)
Raw memory dump, Blender-`.blend`-style — no serialisation, no parsing. Raw memory dump, Blender-`.blend`-style — no serialisation, no parsing.
Stores everything needed to skip the `IfcGeom::Iterator` pass: Stores everything needed to skip the `IfcGeom::Iterator` pass:
``` ```
SidecarHeader (magic "IFVW", version, endian, ...) SidecarHeader (magic "IFVW", version, endian)
uint32_t + uint8_t[] vertex data (12 B/vert quantized; per-mesh basis in MeshInfo) uint32_t + uint8_t[] vertex data (12 B/vert quantized; per-mesh basis in MeshInfo)
uint32_t + uint32_t[] index data (mesh-local) uint32_t + uint32_t[] index data (mesh-local)
uint32_t + MeshInfo[] per-unique-mesh metadata (56 B each, incl. LOD1 slice) uint32_t + MeshInfo[] per-unique-mesh metadata (56 B each, incl. LOD1 slice)
src/ifcviewer/SidecarCache.cpp
+3 -4
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@@ -17,9 +17,9 @@
* * * *
********************************************************************************/ ********************************************************************************/
// v8 layout (all multi-byte fields native-endian; endianness marker in header). // v9 layout (all multi-byte fields native-endian; endianness marker in header).
// //
// SidecarHeader (16 bytes) // SidecarHeader (12 bytes)
// //
// uint32_t num_vertex_bytes // uint32_t num_vertex_bytes
// uint8_t[] vertex data (12 B/vertex: pos u16x3 + oct-normal i8x2 + rgba8) // uint8_t[] vertex data (12 B/vertex: pos u16x3 + oct-normal i8x2 + rgba8)
@@ -46,7 +46,6 @@ struct SidecarHeader {
uint32_t magic; uint32_t magic;
uint32_t version; uint32_t version;
uint32_t endian; uint32_t endian;
uint32_t reserved;
}; };
// foo.ifc -> foo.ifcview // foo.ifc -> foo.ifcview
@@ -87,7 +86,7 @@ bool writeSidecar(const std::string& ifc_path, const SidecarData& data) {
FILE* f = fopen(path.c_str(), "wb"); FILE* f = fopen(path.c_str(), "wb");
if (!f) return false; if (!f) return false;
SidecarHeader hdr = { SIDECAR_MAGIC, SIDECAR_VERSION, SIDECAR_ENDIAN, 0 }; SidecarHeader hdr = { SIDECAR_MAGIC, SIDECAR_VERSION, SIDECAR_ENDIAN };
if (fwrite(&hdr, sizeof(hdr), 1, f) != 1) { fclose(f); return false; } if (fwrite(&hdr, sizeof(hdr), 1, f) != 1) { fclose(f); return false; }
if (!writeVec(f, data.vertices)) { fclose(f); return false; } if (!writeVec(f, data.vertices)) { fclose(f); return false; }
src/ifcviewer/SidecarCache.h
+2 -1
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@@ -45,7 +45,8 @@ static constexpr uint32_t SIDECAR_MAGIC = 0x49465657; // "IFVW"
// on path stem (foo.ifc and foo.ifcdb/ both map to foo.ifcview) so the // on path stem (foo.ifc and foo.ifcdb/ both map to foo.ifcview) so the
// same cache serves either source format. Staleness is user-managed // same cache serves either source format. Staleness is user-managed
// (delete the sidecar to force a rebuild). // (delete the sidecar to force a rebuild).
static constexpr uint32_t SIDECAR_VERSION = 8; // v9 = unused `reserved` field dropped from header (16 B -> 12 B).
static constexpr uint32_t SIDECAR_VERSION = 9;
static constexpr uint32_t SIDECAR_ENDIAN = 0x01020304; static constexpr uint32_t SIDECAR_ENDIAN = 0x01020304;
// Fixed-size element record. Strings are stored as (offset, length) pairs // Fixed-size element record. Strings are stored as (offset, length) pairs