use mmap on BSD without sendfile

io/io_close.c

@@ -1,4 +1,5 @@
 #include <unistd.h>
+#include <sys/mman.h>
 #include "io_internal.h"
 
 void io_close(int64 d) {
@@ -7,6 +8,10 @@ void io_close(int64 d) {
     e->inuse=0;
     io_dontwantread(d);
     io_dontwantwrite(d);
+    if (e->mmapped) {
+      munmap(e->mmapped,e->maplen);
+      e->mmapped=0;
+    }
   }
   close(d);
 }

io/io_sendfile.c

@@ -2,6 +2,8 @@
 #include "io_internal.h"
 #include "havebsdsf.h"
 
+#undef __linux__
+
 #if defined(HAVE_BSDSENDFILE)
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -42,6 +44,7 @@ int64 io_sendfile(int64 s,int64 fd,uint64 off,uint64 n) {
 #else
 
 #include <unistd.h>
+#include <sys/mman.h>
 
 #define BUFSIZE 16384
 
@@ -50,6 +53,46 @@ int64 io_sendfile(int64 out,int64 in,uint64 off,uint64 bytes) {
   int n,m;
   uint64 sent=0;
   io_entry* e=array_get(&io_fds,sizeof(io_entry),out);
+  if (e) {
+    const char* c;
+    long left;
+    do {
+      if (e->mmapped) {
+	/* did we already map the right chunk? */
+	if (off>=e->mapofs && off<e->mapofs+e->maplen)
+	  goto mapok;	/* ok; mmapped the right chunk*/
+	munmap(e->mmapped,e->maplen);
+	e->mmapped=0;
+      }
+      e->mapofs=off&0xffffffffffff0000ull;
+      if (e->mapofs+0xffff>off+bytes)
+	e->maplen=off+bytes-e->mapofs;
+      else
+	e->maplen=0xffff;
+      if ((e->mmapped=mmap(0,e->maplen,PROT_READ,MAP_SHARED,in,e->mapofs))==MAP_FAILED) {
+	e->mmapped=0;
+	goto readwrite;
+      }
+  mapok:
+      c=(const char*)(e->mmapped)+(off&0xffff);
+      left=e->maplen-(off&0xffff);
+      while (left>0) {
+	m=write(out,c,left);
+	if (m==-1) {
+	  e->canwrite=0;
+	  e->next_write=-1;
+	  return errno==EAGAIN?(sent?sent:-1):-3;
+	}
+	if (m==0) return sent;
+	sent+=m;
+	left-=m;
+	bytes-=m;
+	off+=m;
+      }
+    } while (bytes);
+    return sent;
+  }
+readwrite:
   if (lseek(in,off,SEEK_SET) != off)
     return -1;
   while (bytes>0) {

io_internal.h

@@ -25,6 +25,9 @@ typedef struct {
   long next_read;
   long next_write;
   void* cookie;
+  void* mmapped;
+  long maplen;
+  uint64 mapofs;
 #ifdef __MINGW32__
   OVERLAPPED o;
   HANDLE fd;