Validate PPI project layout

src/assets/ppi_header.cpp

@@ -2,6 +2,8 @@
 
 #include "foundation/binary_stream.h"
 
+#include <limits>
+
 namespace pp::assets {
 
 namespace {
@@ -70,4 +72,66 @@ pp::foundation::Result<PpiHeaderInfo> parse_ppi_header(std::span<const std::byte
     return pp::foundation::Result<PpiHeaderInfo>::success(info);
 }
 
+pp::foundation::Result<std::size_t> ppi_thumbnail_byte_size(PpiThumbnailInfo thumbnail) noexcept
+{
+    if (thumbnail.width == 0 || thumbnail.height == 0 || thumbnail.components == 0) {
+        return pp::foundation::Result<std::size_t>::failure(
+            pp::foundation::Status::invalid_argument("PPI thumbnail descriptor is invalid"));
+    }
+
+    const auto width = static_cast<std::uint64_t>(thumbnail.width);
+    const auto height = static_cast<std::uint64_t>(thumbnail.height);
+    const auto components = static_cast<std::uint64_t>(thumbnail.components);
+    if (width > std::numeric_limits<std::uint64_t>::max() / height) {
+        return pp::foundation::Result<std::size_t>::failure(
+            pp::foundation::Status::out_of_range("PPI thumbnail byte size overflows"));
+    }
+
+    const auto pixels = width * height;
+    if (pixels > std::numeric_limits<std::uint64_t>::max() / components) {
+        return pp::foundation::Result<std::size_t>::failure(
+            pp::foundation::Status::out_of_range("PPI thumbnail byte size overflows"));
+    }
+
+    const auto bytes = pixels * components;
+    if (bytes > static_cast<std::uint64_t>(std::numeric_limits<std::size_t>::max())) {
+        return pp::foundation::Result<std::size_t>::failure(
+            pp::foundation::Status::out_of_range("PPI thumbnail byte size exceeds addressable memory"));
+    }
+
+    return pp::foundation::Result<std::size_t>::success(static_cast<std::size_t>(bytes));
+}
+
+pp::foundation::Result<PpiProjectLayout> parse_ppi_project_layout(std::span<const std::byte> bytes) noexcept
+{
+    const auto header = parse_ppi_header(bytes);
+    if (!header) {
+        return pp::foundation::Result<PpiProjectLayout>::failure(header.status());
+    }
+
+    const auto thumbnail_bytes = ppi_thumbnail_byte_size(header.value().thumbnail);
+    if (!thumbnail_bytes) {
+        return pp::foundation::Result<PpiProjectLayout>::failure(thumbnail_bytes.status());
+    }
+
+    if (thumbnail_bytes.value() > std::numeric_limits<std::size_t>::max() - ppi_header_size) {
+        return pp::foundation::Result<PpiProjectLayout>::failure(
+            pp::foundation::Status::out_of_range("PPI thumbnail byte size overflows"));
+    }
+
+    const auto body_offset = ppi_header_size + thumbnail_bytes.value();
+    if (bytes.size() < body_offset) {
+        return pp::foundation::Result<PpiProjectLayout>::failure(
+            pp::foundation::Status::out_of_range("PPI thumbnail payload is truncated"));
+    }
+
+    return pp::foundation::Result<PpiProjectLayout>::success(PpiProjectLayout {
+        .header = header.value(),
+        .thumbnail_offset = ppi_header_size,
+        .thumbnail_bytes = thumbnail_bytes.value(),
+        .body_offset = body_offset,
+        .body_bytes = bytes.size() - body_offset,
+    });
+}
+
 }

src/assets/ppi_header.h

@@ -34,7 +34,20 @@ struct PpiHeaderInfo {
     PpiThumbnailInfo thumbnail;
 };
 
+struct PpiProjectLayout {
+    PpiHeaderInfo header;
+    std::size_t thumbnail_offset = 0;
+    std::size_t thumbnail_bytes = 0;
+    std::size_t body_offset = 0;
+    std::size_t body_bytes = 0;
+};
+
 [[nodiscard]] pp::foundation::Result<PpiHeaderInfo> parse_ppi_header(
     std::span<const std::byte> bytes) noexcept;
 
+[[nodiscard]] pp::foundation::Result<std::size_t> ppi_thumbnail_byte_size(PpiThumbnailInfo thumbnail) noexcept;
+
+[[nodiscard]] pp::foundation::Result<PpiProjectLayout> parse_ppi_project_layout(
+    std::span<const std::byte> bytes) noexcept;
+
 }