base: compact returns the change in writer length

internal/cgen/base/io-public.h

@@ -31,8 +31,8 @@ typedef struct wuffs_base__io_buffer__struct {
 
 #ifdef __cplusplus
  inline bool is_valid() const;
- inline void compact();
- inline void compact_retaining(uint64_t history_retain_length);
+ inline size_t compact();
+ inline size_t compact_retaining(uint64_t history_retain_length);
  inline size_t reader_length() const;
  inline uint8_t* reader_pointer() const;
  inline uint64_t reader_position() const;
@@ -151,18 +151,22 @@ wuffs_base__io_buffer__is_valid(const wuffs_base__io_buffer* buf) {
 
 // wuffs_base__io_buffer__compact moves any written but unread bytes to the
 // start of the buffer.
-static inline void //
+//
+// It returns the increase in the writer length: how much meta.wi fell by.
+static inline size_t //
 wuffs_base__io_buffer__compact(wuffs_base__io_buffer* buf) {
  if (!buf || (buf->meta.ri == 0)) {
- return;
+ return 0;
  }
+ size_t old_ri = buf->meta.ri;
  buf->meta.pos = wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.ri);
  size_t new_wi = buf->meta.wi - buf->meta.ri;
  if (new_wi != 0) {
  memmove(buf->data.ptr, buf->data.ptr + buf->meta.ri, new_wi);
  }
  buf->meta.wi = new_wi;
  buf->meta.ri = 0;
+ return old_ri;
 }
 
 // wuffs_base__io_buffer__compact_retaining moves any written but unread bytes
@@ -171,6 +175,8 @@ wuffs_base__io_buffer__compact(wuffs_base__io_buffer* buf) {
 // It is therefore a no-op if history_retain_length is UINT64_MAX. A
 // postcondition is that buf->meta.ri == H.
 //
+// It returns the increase in the writer length: how much meta.wi fell by.
+//
 // wuffs_base__io_buffer__compact_retaining(0) is equivalent to
 // wuffs_base__io_buffer__compact().
 //
@@ -184,16 +190,16 @@ wuffs_base__io_buffer__compact(wuffs_base__io_buffer* buf) {
 //
 // Then, depending on history_retain_length, the resultant buf would be:
 //
-// HRL = 0 defgh????? ri = 0 wi = 5 pos = 903
-// HRL = 1 cdefgh???? ri = 1 wi = 6 pos = 902
-// HRL = 2 bcdefgh??? ri = 2 wi = 7 pos = 901
-// HRL = 3 abcdefgh?? ri = 3 wi = 8 pos = 900
-// HRL = 4+ abcdefgh?? ri = 3 wi = 8 pos = 900
-static inline void //
+// HRL = 0 defgh????? ri = 0 wi = 5 pos = 903 return = 3
+// HRL = 1 cdefgh???? ri = 1 wi = 6 pos = 902 return = 2
+// HRL = 2 bcdefgh??? ri = 2 wi = 7 pos = 901 return = 1
+// HRL = 3 abcdefgh?? ri = 3 wi = 8 pos = 900 return = 0
+// HRL = 4+ abcdefgh?? ri = 3 wi = 8 pos = 900 return = 0
+static inline size_t //
 wuffs_base__io_buffer__compact_retaining(wuffs_base__io_buffer* buf,
  uint64_t history_retain_length) {
  if (!buf || (buf->meta.ri == 0)) {
- return;
+ return 0;
  }
  size_t old_ri = buf->meta.ri;
  size_t new_ri = (size_t)(wuffs_base__u64__min(old_ri, history_retain_length));
@@ -205,6 +211,7 @@ wuffs_base__io_buffer__compact_retaining(wuffs_base__io_buffer* buf,
  }
  buf->meta.wi = new_wi;
  buf->meta.ri = new_ri;
+ return memmove_start;
 }
 
 static inline size_t //
@@ -260,14 +267,14 @@ wuffs_base__io_buffer::is_valid() const {
  return wuffs_base__io_buffer__is_valid(this);
 }
 
-inline void //
+inline size_t //
 wuffs_base__io_buffer::compact() {
- wuffs_base__io_buffer__compact(this);
+ return wuffs_base__io_buffer__compact(this);
 }
 
-inline void //
+inline size_t //
 wuffs_base__io_buffer::compact_retaining(uint64_t history_retain_length) {
- wuffs_base__io_buffer__compact_retaining(this, history_retain_length);
+ return wuffs_base__io_buffer__compact_retaining(this, history_retain_length);
 }
 
 inline size_t //

internal/cgen/base/token-public.h

@@ -340,8 +340,8 @@ typedef struct wuffs_base__token_buffer__struct {
 
 #ifdef __cplusplus
  inline bool is_valid() const;
- inline void compact();
- inline void compact_retaining(uint64_t history_retain_length);
+ inline size_t compact();
+ inline size_t compact_retaining(uint64_t history_retain_length);
  inline uint64_t reader_length() const;
  inline wuffs_base__token* reader_pointer() const;
  inline wuffs_base__slice_token reader_slice() const;
@@ -436,11 +436,14 @@ wuffs_base__token_buffer__is_valid(const wuffs_base__token_buffer* buf) {
 
 // wuffs_base__token_buffer__compact moves any written but unread tokens to the
 // start of the buffer.
-static inline void //
+//
+// It returns the increase in the writer length: how much meta.wi fell by.
+static inline size_t //
 wuffs_base__token_buffer__compact(wuffs_base__token_buffer* buf) {
  if (!buf || (buf->meta.ri == 0)) {
- return;
+ return 0;
  }
+ size_t old_ri = buf->meta.ri;
  buf->meta.pos = wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.ri);
  size_t new_wi = buf->meta.wi - buf->meta.ri;
  if (new_wi != 0) {
@@ -449,6 +452,7 @@ wuffs_base__token_buffer__compact(wuffs_base__token_buffer* buf) {
  }
  buf->meta.wi = new_wi;
  buf->meta.ri = 0;
+ return old_ri;
 }
 
 // wuffs_base__token_buffer__compact_retaining moves any written but unread
@@ -457,6 +461,8 @@ wuffs_base__token_buffer__compact(wuffs_base__token_buffer* buf) {
 // history_retain_length). It is therefore a no-op if history_retain_length is
 // UINT64_MAX. A postcondition is that buf->meta.ri == H.
 //
+// It returns the increase in the writer length: how much meta.wi fell by.
+//
 // wuffs_base__token_buffer__compact_retaining(0) is equivalent to
 // wuffs_base__token_buffer__compact().
 //
@@ -470,16 +476,16 @@ wuffs_base__token_buffer__compact(wuffs_base__token_buffer* buf) {
 //
 // Then, depending on history_retain_length, the resultant buf would be:
 //
-// HRL = 0 defgh????? ri = 0 wi = 5 pos = 903
-// HRL = 1 cdefgh???? ri = 1 wi = 6 pos = 902
-// HRL = 2 bcdefgh??? ri = 2 wi = 7 pos = 901
-// HRL = 3 abcdefgh?? ri = 3 wi = 8 pos = 900
-// HRL = 4+ abcdefgh?? ri = 3 wi = 8 pos = 900
-static inline void //
+// HRL = 0 defgh????? ri = 0 wi = 5 pos = 903 return = 3
+// HRL = 1 cdefgh???? ri = 1 wi = 6 pos = 902 return = 2
+// HRL = 2 bcdefgh??? ri = 2 wi = 7 pos = 901 return = 1
+// HRL = 3 abcdefgh?? ri = 3 wi = 8 pos = 900 return = 0
+// HRL = 4+ abcdefgh?? ri = 3 wi = 8 pos = 900 return = 0
+static inline size_t //
 wuffs_base__token_buffer__compact_retaining(wuffs_base__token_buffer* buf,
  uint64_t history_retain_length) {
  if (!buf || (buf->meta.ri == 0)) {
- return;
+ return 0;
  }
  size_t old_ri = buf->meta.ri;
  size_t new_ri = (size_t)(wuffs_base__u64__min(old_ri, history_retain_length));
@@ -492,6 +498,7 @@ wuffs_base__token_buffer__compact_retaining(wuffs_base__token_buffer* buf,
  }
  buf->meta.wi = new_wi;
  buf->meta.ri = new_ri;
+ return memmove_start;
 }
 
 static inline uint64_t //
@@ -547,14 +554,15 @@ wuffs_base__token_buffer::is_valid() const {
  return wuffs_base__token_buffer__is_valid(this);
 }
 
-inline void //
+inline size_t //
 wuffs_base__token_buffer::compact() {
- wuffs_base__token_buffer__compact(this);
+ return wuffs_base__token_buffer__compact(this);
 }
 
-inline void //
+inline size_t //
 wuffs_base__token_buffer::compact_retaining(uint64_t history_retain_length) {
- wuffs_base__token_buffer__compact_retaining(this, history_retain_length);
+ return wuffs_base__token_buffer__compact_retaining(this,
+ history_retain_length);
 }
 
 inline uint64_t //

internal/cgen/drop-in/stb.c

@@ -169,9 +169,7 @@ wuffs_drop_in__stb__load1( //
  return NULL;
  }
 
- size_t wl = wuffs_base__io_buffer__writer_length(srcbuf);
- wuffs_base__io_buffer__compact(srcbuf);
- if (wl >= wuffs_base__io_buffer__writer_length(srcbuf)) {
+ if (wuffs_base__io_buffer__compact(srcbuf) <= 0) {
  wuffs_drop_in__stb__g_failure_reason = "I/O buffer is too small";
  return NULL;
  }
@@ -238,9 +236,7 @@ wuffs_drop_in__stb__load1( //
  return NULL;
  }
 
- size_t wl = wuffs_base__io_buffer__writer_length(srcbuf);
- wuffs_base__io_buffer__compact(srcbuf);
- if (wl >= wuffs_base__io_buffer__writer_length(srcbuf)) {
+ if (wuffs_base__io_buffer__compact(srcbuf) <= 0) {
  free(workbuf_ptr);
  free(pixbuf_ptr);
  wuffs_drop_in__stb__g_failure_reason = "I/O buffer is too small";