grpc/include/grpc/support/slice.h

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 *
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#ifndef GRPC_SUPPORT_SLICE_H
#define GRPC_SUPPORT_SLICE_H

#include <grpc/support/sync.h>

#include <stddef.h>

#ifdef __cplusplus
extern "C" {
#endif

/* Slice API

   A slice represents a contiguous reference counted array of bytes.
   It is cheap to take references to a slice, and it is cheap to create a
   slice pointing to a subset of another slice.

   The data-structure for slices is exposed here to allow non-gpr code to
   build slices from whatever data they have available.

   When defining interfaces that handle slices, care should be taken to define
   reference ownership semantics (who should call unref?) and mutability
   constraints (is the callee allowed to modify the slice?) */

/* Reference count container for gpr_slice. Contains function pointers to
   increment and decrement reference counts. Implementations should cleanup
   when the reference count drops to zero.
   Typically client code should not touch this, and use gpr_slice_malloc,
   gpr_slice_new, or gpr_slice_new_with_len instead. */
typedef struct gpr_slice_refcount {
  void (*ref)(void *);
  void (*unref)(void *);
} gpr_slice_refcount;

#define GPR_SLICE_INLINED_SIZE (sizeof(size_t) + sizeof(gpr_uint8 *) - 1)

/* A gpr_slice s, if initialized, represents the byte range
   s.bytes[0..s.length-1].

   It can have an associated ref count which has a destruction routine to be run
   when the ref count reaches zero (see gpr_slice_new() and grp_slice_unref()).
   Multiple gpr_slice values may share a ref count.

   If the slice does not have a refcount, it represents an inlined small piece
   of data that is copied by value. */
typedef struct gpr_slice {
  struct gpr_slice_refcount *refcount;
  union {
    struct {
      gpr_uint8 *bytes;
      size_t length;
    } refcounted;
    struct {
      gpr_uint8 length;
      gpr_uint8 bytes[GPR_SLICE_INLINED_SIZE];
    } inlined;
  } data;
} gpr_slice;

#define GPR_SLICE_START_PTR(slice)                  \
  ((slice).refcount ? (slice).data.refcounted.bytes \
                    : (slice).data.inlined.bytes)
#define GPR_SLICE_LENGTH(slice)                      \
  ((slice).refcount ? (slice).data.refcounted.length \
                    : (slice).data.inlined.length)
#define GPR_SLICE_SET_LENGTH(slice, newlen)                               \
  ((slice).refcount ? ((slice).data.refcounted.length = (size_t)(newlen)) \
                    : ((slice).data.inlined.length = (gpr_uint8)(newlen)))
#define GPR_SLICE_END_PTR(slice) \
  GPR_SLICE_START_PTR(slice) + GPR_SLICE_LENGTH(slice)
#define GPR_SLICE_IS_EMPTY(slice) (GPR_SLICE_LENGTH(slice) == 0)

/* Increment the refcount of s. Requires slice is initialized.
   Returns s. */
gpr_slice gpr_slice_ref(gpr_slice s);

/* Decrement the ref count of s.  If the ref count of s reaches zero, all
   slices sharing the ref count are destroyed, and considered no longer
   initialized.  If s is ultimately derived from a call to gpr_slice_new(start,
   len, dest) where dest!=NULL , then (*dest)(start) is called, else if s is
   ultimately derived from a call to gpr_slice_new_with_len(start, len, dest)
   where dest!=NULL , then (*dest)(start, len).  Requires s initialized.  */
void gpr_slice_unref(gpr_slice s);

/* Create a slice pointing at some data. Calls malloc to allocate a refcount
   for the object, and arranges that destroy will be called with the pointer
   passed in at destruction. */
gpr_slice gpr_slice_new(void *p, size_t len, void (*destroy)(void *));

/* Equivalent to gpr_slice_new, but with a two argument destroy function that
   also takes the slice length. */
gpr_slice gpr_slice_new_with_len(void *p, size_t len,
                                 void (*destroy)(void *, size_t));

/* Equivalent to gpr_slice_new(malloc(len), len, free), but saves one malloc()
   call.
   Aborts if malloc() fails. */
gpr_slice gpr_slice_malloc(size_t length);

/* Create a slice by copying a string.
   Does not preserve null terminators.
   Equivalent to:
     size_t len = strlen(source);
     gpr_slice slice = gpr_slice_malloc(len);
     memcpy(slice->data, source, len); */
gpr_slice gpr_slice_from_copied_string(const char *source);

/* Create a slice by copying a buffer.
   Equivalent to:
     gpr_slice slice = gpr_slice_malloc(len);
     memcpy(slice->data, source, len); */
gpr_slice gpr_slice_from_copied_buffer(const char *source, size_t len);

/* Create a slice pointing to constant memory */
gpr_slice gpr_slice_from_static_string(const char *source);

/* Return a result slice derived from s, which shares a ref count with s, where
   result.data==s.data+begin, and result.length==end-begin.
   The ref count of s is increased by one.
   Requires s initialized, begin <= end, begin <= s.length, and
   end <= source->length. */
gpr_slice gpr_slice_sub(gpr_slice s, size_t begin, size_t end);

/* The same as gpr_slice_sub, but without altering the ref count */
gpr_slice gpr_slice_sub_no_ref(gpr_slice s, size_t begin, size_t end);

/* Splits s into two: modifies s to be s[0:split], and returns a new slice,
   sharing a refcount with s, that contains s[split:s.length].
   Requires s intialized, split <= s.length */
gpr_slice gpr_slice_split_tail(gpr_slice *s, size_t split);

/* Splits s into two: modifies s to be s[split:s.length], and returns a new
   slice, sharing a refcount with s, that contains s[0:split].
   Requires s intialized, split <= s.length */
gpr_slice gpr_slice_split_head(gpr_slice *s, size_t split);

gpr_slice gpr_empty_slice(void);

/* Returns <0 if a < b, ==0 if a == b, >0 if a > b
   The order is arbitrary, and is not guaranteed to be stable across different
   versions of the API. */
int gpr_slice_cmp(gpr_slice a, gpr_slice b);
int gpr_slice_str_cmp(gpr_slice a, const char *b);

/* Returns a c-string representation of a slice. Useful for logging or debugging
   purposes only. The string representation can change in future */
char *gpr_slice_to_cstring(gpr_slice slice);

#ifdef __cplusplus
}
#endif

#endif /* GRPC_SUPPORT_SLICE_H */