1 files changed, 61 insertions, 0 deletions
diff --git a/prism/util/pm_string.h b/prism/util/pm_string.h
new file mode 100644
index 0000000000..bcdf8b66d9
--- /dev/null
+++ b/prism/util/pm_string.h
@@ -0,0 +1,61 @@
+#ifndef YARP_STRING_H
+#define YARP_STRING_H
+
+#include "yarp/defines.h"
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+// This struct represents a string value.
+typedef struct {
+    enum { YP_STRING_SHARED, YP_STRING_OWNED, YP_STRING_CONSTANT, YP_STRING_MAPPED } type;
+    const uint8_t *source;
+    size_t length;
+} yp_string_t;
+
+#define YP_EMPTY_STRING ((yp_string_t) { .type = YP_STRING_CONSTANT, .source = NULL, .length = 0 })
+
+// Initialize a shared string that is based on initial input.
+void yp_string_shared_init(yp_string_t *string, const uint8_t *start, const uint8_t *end);
+
+// Initialize an owned string that is responsible for freeing allocated memory.
+void yp_string_owned_init(yp_string_t *string, uint8_t *source, size_t length);
+
+// Initialize a constant string that doesn't own its memory source.
+void yp_string_constant_init(yp_string_t *string, const char *source, size_t length);
+
+// Read the file indicated by the filepath parameter into source and load its
+// contents and size into the given yp_string_t.
+// The given yp_string_t should be freed using yp_string_free() when it is no longer used.
+//
+// We want to use demand paging as much as possible in order to avoid having to
+// read the entire file into memory (which could be detrimental to performance
+// for large files). This means that if we're on windows we'll use
+// `MapViewOfFile`, on POSIX systems that have access to `mmap` we'll use
+// `mmap`, and on other POSIX systems we'll use `read`.
+YP_EXPORTED_FUNCTION bool yp_string_mapped_init(yp_string_t *string, const char *filepath);
+
+// Returns the memory size associated with the string.
+size_t yp_string_memsize(const yp_string_t *string);
+
+// Ensure the string is owned. If it is not, then reinitialize it as owned and
+// copy over the previous source.
+void yp_string_ensure_owned(yp_string_t *string);
+
+// Returns the length associated with the string.
+YP_EXPORTED_FUNCTION size_t yp_string_length(const yp_string_t *string);
+
+// Returns the start pointer associated with the string.
+YP_EXPORTED_FUNCTION const uint8_t * yp_string_source(const yp_string_t *string);
+
+// Free the associated memory of the given string.
+YP_EXPORTED_FUNCTION void yp_string_free(yp_string_t *string);
+
+// Returns the size of the yp_string_t struct. This is necessary to allocate the
+// correct amount of memory in the FFI backend.
+YP_EXPORTED_FUNCTION size_t yp_string_sizeof(void);
+
+#endif // YARP_STRING_H