Add string view API

3 files changed, 113 insertions, 3 deletions

diff --git a/include/zix/attributes.h b/include/zix/attributes.h
index 1fe1183..b076fa7 100644
--- a/include/zix/attributes.h
+++ b/include/zix/attributes.h
@@ -34,13 +34,15 @@
 
 // GCC function attributes
 #ifdef __GNUC__
+#  define ZIX_ALWAYS_INLINE_FUNC __attribute__((always_inline))
 #  define ZIX_PURE_FUNC __attribute__((pure))
 #  define ZIX_CONST_FUNC __attribute__((const))
 #  define ZIX_MALLOC_FUNC __attribute__((malloc))
 #else
-#  define ZIX_PURE_FUNC   ///< Only reads memory
-#  define ZIX_CONST_FUNC  ///< Only reads its parameters
-#  define ZIX_MALLOC_FUNC ///< Allocates memory
+#  define ZIX_ALWAYS_INLINE_FUNC ///< Should absolutely always be inlined
+#  define ZIX_PURE_FUNC          ///< Only reads memory
+#  define ZIX_CONST_FUNC         ///< Only reads its parameters
+#  define ZIX_MALLOC_FUNC        ///< Allocates memory
 #endif
 
 /// A pure function in the public API that only reads memory
diff --git a/include/zix/string_view.h b/include/zix/string_view.h
new file mode 100644
index 0000000..f4cd6c2
--- /dev/null
+++ b/include/zix/string_view.h
@@ -0,0 +1,107 @@
+// Copyright 2011-2021 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#ifndef ZIX_STRING_VIEW_H
+#define ZIX_STRING_VIEW_H
+
+#include "zix/allocator.h"
+#include "zix/attributes.h"
+
+#include <stddef.h>
+#include <string.h>
+
+ZIX_BEGIN_DECLS
+
+/**
+   @defgroup zix_string_view String View
+   @ingroup zix_utilities
+   @{
+*/
+
+/**
+   An immutable slice of a string.
+
+   This type is used for many string parameters, to allow referring to slices
+   of strings in-place and to avoid redundant string measurement.
+*/
+typedef struct {
+  const char* ZIX_NONNULL data;   ///< Pointer to the first character
+  size_t                  length; ///< Length of string in bytes
+} ZixStringView;
+
+/// Return a view of an empty string
+ZIX_ALWAYS_INLINE_FUNC
+ZIX_CONST_FUNC
+static inline ZixStringView
+zix_empty_string(void)
+{
+  const ZixStringView view = {"", 0U};
+  return view;
+}
+
+/**
+   Return a view of a substring, or a premeasured string.
+
+   This makes either a view of a slice of a string (which may not be null
+   terminated), or a view of a string that has already been measured.  This is
+   faster than zix_string() for dynamic strings since it does not call
+   `strlen`, so should be used when the length of the string is already known.
+
+   @param str Pointer to the start of the substring.
+
+   @param len Length of the substring in bytes, not including the trailing null
+   terminator if present.
+*/
+ZIX_ALWAYS_INLINE_FUNC
+ZIX_CONST_FUNC
+static inline ZixStringView
+zix_substring(const char* const ZIX_NONNULL str, const size_t len)
+{
+  const ZixStringView view = {str, len};
+  return view;
+}
+
+/**
+   Return a view of an entire string by measuring it.
+
+   This makes a view of the given string by measuring it with `strlen`.
+
+   @param str Pointer to the start of a null-terminated C string, or null.
+*/
+ZIX_ALWAYS_INLINE_FUNC
+ZIX_PURE_FUNC
+static inline ZixStringView
+zix_string(const char* const ZIX_NONNULL str)
+{
+  const ZixStringView view = {str, strlen(str)};
+  return view;
+}
+
+/**
+   Return a view of an entire string by measuring it.
+
+   This makes a view of the given string by measuring it with `strlen`.
+
+   @param str Pointer to the start of a null-terminated C string, or null.
+*/
+ZIX_PURE_FUNC
+static inline ZixStringView
+zix_optional_string(const char* const ZIX_NULLABLE str)
+{
+  return str ? zix_string(str) : zix_empty_string();
+}
+
+/**
+   Copy a string view into a newly allocated null-terminated string.
+*/
+ZIX_API
+char* ZIX_ALLOCATED
+zix_string_view_copy(ZixAllocator* ZIX_NULLABLE allocator, ZixStringView view);
+
+/**
+   @}
+*/
+
+ZIX_END_DECLS
+
+#endif // ZIX_STRING_VIEW_H
diff --git a/include/zix/zix.h b/include/zix/zix.h
index 02ab31f..223d1dc 100644
--- a/include/zix/zix.h
+++ b/include/zix/zix.h
@@ -20,6 +20,7 @@
 #include "zix/digest.h"
 #include "zix/function_types.h"
 #include "zix/status.h"
+#include "zix/string_view.h"
 
 /**
    @}