[k2] add mmap, madvise (#1514)

Author: denisichh

runtime-light/k2-platform/k2-api.h

@@ -216,6 +216,17 @@ inline size_t pread(k2::descriptor descriptor, std::span<std::byte> buffer, uint
   return k2_pread(descriptor, buffer.size(), static_cast<void*>(buffer.data()), offset);
 }
 
+inline void* mmap(k2::descriptor* md, void* addr, size_t length, int32_t prot, int32_t flags, k2::descriptor fd, uint64_t offset) noexcept {
+  return k2_mmap(md, addr, length, prot, flags, fd, offset);
+}
+
+inline std::expected<void, int32_t> madvise(void* addr, size_t length, int32_t advise) noexcept {
+  if (auto error_code{k2_madvise(addr, length, advise)}; error_code != k2::errno_ok) [[unlikely]] {
+    return std::unexpected{error_code};
+  }
+  return {};
+}
+
 inline void please_shutdown(k2::descriptor descriptor) noexcept {
   k2_please_shutdown(descriptor);
 }

runtime-light/k2-platform/k2-header.h

@@ -356,6 +356,19 @@ size_t k2_read(uint64_t stream_d, size_t buf_len, void* buf);
  */
 size_t k2_pread(uint64_t stream_d, size_t buf_len, void* buf, uint64_t offset);
 
+/**
+ * Semantically equivalent to libc's `mmap` function.
+ *
+ * @param `md` A pointer to a `uint64_t` where the mmap descriptor will be stored upon success.
+ * @param `addr` Must always be nullptr.
+ */
+void* k2_mmap(uint64_t* md, void* addr, size_t length, int32_t prot, int32_t flags, uint64_t fd, uint64_t offset);
+
+/**
+ * Semantically equivalent to libc's `madvise` function.
+ */
+int32_t k2_madvise(void* addr, size_t length, int32_t advise);
+
 /**
  * Sets `StreamStatus.please_whutdown_write=true` for the component on the
  * opposite side (does not affect `StreamStatus` on your side).