diff --git a/src/StreamBuffer.cc b/src/StreamBuffer.cc
index 1bbb525..b08e248 100644
--- a/src/StreamBuffer.cc
+++ b/src/StreamBuffer.cc
@@ -30,8 +30,10 @@
 #define vsnprintf epicsVsnprintf
 #endif
 
+#define S PRINTF_SIZE_T_PREFIX
+
 void StreamBuffer::
-init(const void* s, long minsize)
+init(const void* s, size_t minsize)
 {
     len = 0;
     offs = 0;
@@ -62,11 +64,11 @@ init(const void* s, long minsize)
 
 
 void StreamBuffer::
-grow(long minsize)
+grow(size_t minsize)
 {
     // make space for minsize + 1 (for termination) bytes
     char* newbuffer;
-    long newcap;
+    size_t newcap;
 #ifdef EXPLODE
     if (minsize > 1000000)
     {
@@ -117,12 +119,12 @@ grow(long minsize)
 }
 
 StreamBuffer& StreamBuffer::
-append(const void* s, long size)
+append(const void* s, ssize_t size)
 {
     if (size <= 0)
     {
         // append negative number of bytes? let's delete some
-        if (size < -len) size = -len;
+        if ((size_t)-size > len) size = -len;
         memset (buffer+offs+len+size, 0, -size);
     }
     else
@@ -135,7 +137,7 @@ append(const void* s, long size)
 }
 
 long int StreamBuffer::
-find(const void* m, long size, long start) const
+find(const void* m, size_t size, ssize_t start) const
 {
     if (start < 0)
     {
@@ -147,7 +149,7 @@ find(const void* m, long size, long start) const
     const char* s = static_cast<const char*>(m);
     char* b = buffer+offs;
     char* p = b+start;
-    long i;
+    size_t i;
     while ((p = static_cast<char*>(memchr(p, s[0], b-p+len-size+1))))
     {
         for (i = 1; i < size; i++)
@@ -161,7 +163,7 @@ next:   p++;
 }
 
 StreamBuffer& StreamBuffer::
-replace(long remstart, long remlen, const void* ins, long inslen)
+replace(ssize_t remstart, ssize_t remlen, const void* ins, ssize_t inslen)
 {
     if (remstart < 0)
     {
@@ -187,12 +189,12 @@ replace(long remstart, long remlen, const void* ins, long inslen)
         remlen += remstart;
         remstart = 0;
     }
-    if (remstart > len)
+    if ((size_t)remstart > len)
     {
         // remove begins after bufferend
         remstart = len;
     }
-    if (remlen >= len-remstart)
+    if ((size_t)remlen >= len-remstart)
     {
         // truncate remove after bufferend
         remlen = len-remstart;
@@ -205,12 +207,12 @@ replace(long remstart, long remlen, const void* ins, long inslen)
         return *this;
     }
     if (inslen < 0) inslen = 0;
-    long remend = remstart+remlen;
-    long newlen = len+inslen-remlen;
+    size_t remend = remstart+remlen;
+    size_t newlen = len+inslen-remlen;
     if (cap <= newlen)
     {
         // buffer too short
-        long newcap;
+        size_t newcap;
         for (newcap = sizeof(local)*2; newcap <= newlen; newcap *= 2);
         char* newbuffer = new char[newcap];
         memcpy(newbuffer, buffer+offs, remstart);
@@ -251,13 +253,13 @@ StreamBuffer& StreamBuffer::
 print(const char* fmt, ...)
 {
     va_list va;
-    int printed;
+    ssize_t printed;
     while (1)
     {
         va_start(va, fmt);
         printed = vsnprintf(buffer+offs+len, cap-offs-len, fmt, va);
         va_end(va);
-        if (printed > -1 && printed < (int)(cap-offs-len))
+        if (printed > -1 && printed < (ssize_t)(cap-offs-len))
         {
             len += printed;
             return *this;
@@ -267,9 +269,9 @@ print(const char* fmt, ...)
     }
 }
 
-StreamBuffer StreamBuffer::expand(long start, long length) const
+StreamBuffer StreamBuffer::expand(ssize_t start, ssize_t length) const
 {
-    long end;
+    size_t end;
     if (start < 0)
     {
         start += len;
@@ -289,7 +291,7 @@ StreamBuffer StreamBuffer::expand(long start, long length) const
     StreamBuffer result((end-start)*2);
     start += offs;
     end += offs;
-    long i;
+    size_t i;
     char c;
     for (i = start; i < end; i++)
     {
@@ -311,8 +313,8 @@ dump() const
 {
     StreamBuffer result(256+cap*5);
     result.append("\033[0m");
-    long i;
-    result.print("%ld,%ld,%ld:\033[37m", offs, len, cap);
+    size_t i;
+    result.print("%"S"d,%"S"d,%"S"d:\033[37m", offs, len, cap);
     for (i = 0; i < cap; i++)
     {
         if (i == offs) result.append("\033[34m[\033[0m");
diff --git a/src/StreamBuffer.h b/src/StreamBuffer.h
index a081b5b..2dd5d58 100644
--- a/src/StreamBuffer.h
+++ b/src/StreamBuffer.h
@@ -21,6 +21,7 @@
 #define StreamBuffer_h
 
 #include <string.h>
+#include <stdlib.h>
 
 #ifndef __GNUC__
 #define __attribute__(x)
@@ -29,17 +30,17 @@
 class StreamBuffer
 {
     char local[64];
-    long len;
-    long cap;
-    long offs;
+    size_t len;
+    size_t cap;
+    size_t offs;
     char* buffer;
 
-    void init(const void* s, long minsize);
+    void init(const void* s, size_t minsize);
 
-    void check(long size)
+    void check(size_t size)
         {if (len+offs+size >= cap) grow(len+size);}
 
-    void grow(long minsize);
+    void grow(size_t minsize);
 
 public:
     // Hints:
@@ -54,7 +55,7 @@ public:
     StreamBuffer()
         {init(NULL, 0);}
 
-    StreamBuffer(const void* s, long size)
+    StreamBuffer(const void* s, size_t size)
         {init(s, size);}
 
     StreamBuffer(const char* s)
@@ -63,24 +64,24 @@ public:
     StreamBuffer(const StreamBuffer& s)
         {init(s.buffer+s.offs, s.len);}
 
-    StreamBuffer(long size)
+    StreamBuffer(size_t size)
         {init(NULL, size);}
 
     ~StreamBuffer()
         {if (buffer != local) delete buffer;}
 
     // operator (): get char* pointing to index
-    const char* operator()(long index=0) const
+    const char* operator()(ssize_t index=0) const
         {return buffer+offs+(index<0?index+len:index);}
 
-    char* operator()(long index=0)
+    char* operator()(ssize_t index=0)
         {return buffer+offs+(index<0?index+len:index);}
 
     // operator []: get byte at index
-    char operator[](long index) const
+    char operator[](ssize_t index) const
         {return buffer[offs+(index<0?index+len:index)];}
 
-    char& operator[](long index)
+    char& operator[](ssize_t index)
         {return buffer[offs+(index<0?index+len:index)];}
 
     // cast to bool: not empty?
@@ -88,11 +89,11 @@ public:
         {return len>0;}
 
     // length: get current data length
-    long length() const
+    ssize_t length() const
         {return len;}
 
     // capacity: get current max data length (spare one byte for end)
-    long capacity() const
+    ssize_t capacity() const
         {return cap-1;}
 
     // end: get pointer to byte after last data byte
@@ -105,19 +106,19 @@ public:
 
     // reserve: reserve size bytes of memory and return
     // pointer to that memory (for copying something to it)
-    char* reserve(long size)
+    char* reserve(size_t size)
         {check(size); char* p=buffer+offs+len; len+=size; return p;}
 
     // append: append data at the end of the buffer
     StreamBuffer& append(char c)
         {check(1); buffer[offs+len++]=c; return *this;}
 
-    StreamBuffer& append(char c, long count)
+    StreamBuffer& append(char c, ssize_t count)
         {if (count < 0) truncate(count);
          else {check(count); memset(buffer+offs+len, c, count); len+=count;}
          return *this;}
 
-    StreamBuffer& append(const void* s, long size);
+    StreamBuffer& append(const void* s, ssize_t size);
 
     StreamBuffer& append(const char* s)
         {return append(s, s?strlen(s):0);}
@@ -136,7 +137,7 @@ public:
         {return append(s);}
 
     // set: clear buffer and fill with new data
-    StreamBuffer& set(const void* s, long size)
+    StreamBuffer& set(const void* s, size_t size)
         {clear(); return append(s, size);}
 
     StreamBuffer& set(const char* s)
@@ -154,61 +155,61 @@ public:
 
     // replace: delete part of buffer (pos/length) and insert new data
     StreamBuffer& replace(
-        long pos, long length, const void* s, long size);
+        ssize_t pos, ssize_t length, const void* s, ssize_t size);
 
-    StreamBuffer& replace(long pos, long length, const char* s)
+    StreamBuffer& replace(ssize_t pos, ssize_t length, const char* s)
         {return replace(pos, length, s, s?strlen(s):0);}
 
-    StreamBuffer& replace(long pos, long length, const StreamBuffer& s)
+    StreamBuffer& replace(ssize_t pos, ssize_t length, const StreamBuffer& s)
         {return replace(pos, length, s.buffer+s.offs, s.len);}
 
     // remove: delete from start/pos
-    StreamBuffer& remove(long pos, long length)
+    StreamBuffer& remove(ssize_t pos, ssize_t length)
         {return replace(pos, length, NULL, 0);}
 
     // remove from start: no memset, no function call, fast!
-    StreamBuffer& remove(long length)
+    StreamBuffer& remove(size_t length)
         {if (length>len) length=len;
          offs+=length; len-=length; return *this;}
 
     // truncate: delete end of buffer
-    StreamBuffer& truncate(long pos)
+    StreamBuffer& truncate(ssize_t pos)
         {return replace(pos, len, NULL, 0);}
 
     // insert: insert new data into buffer
-    StreamBuffer& insert(long pos, const void* s, long size)
+    StreamBuffer& insert(ssize_t pos, const void* s, ssize_t size)
         {return replace(pos, 0, s, size);}
 
-    StreamBuffer& insert(long pos, const char* s)
+    StreamBuffer& insert(ssize_t pos, const char* s)
         {return replace(pos, 0, s, s?strlen(s):0);}
 
-    StreamBuffer& insert(long pos, const StreamBuffer& s)
+    StreamBuffer& insert(ssize_t pos, const StreamBuffer& s)
         {return replace(pos, 0, s.buffer+s.offs, s.len);}
 
-    StreamBuffer& insert(long pos, char c)
+    StreamBuffer& insert(ssize_t pos, char c)
         {return replace(pos, 0, &c, 1);}
 
     StreamBuffer& print(const char* fmt, ...)
         __attribute__ ((format(printf,2,3)));
 
     // find: get index of data in buffer or -1
-    long find(char c, long start=0) const
+    long find(char c, ssize_t start=0) const
         {char* p;
          return (p = static_cast<char*>(
             memchr(buffer+offs+(start<0?start+len:start),
                 c, start<0?-start:len-start)))?
             p-(buffer+offs) : -1;}
 
-    long find(const void* s, long size, long start=0) const;
+    long find(const void* s, size_t size, ssize_t start=0) const;
 
-    long find(const char* s, long start=0) const
+    long find(const char* s, ssize_t start=0) const
         {return find(s, s?strlen(s):0, start);}
 
-    long int find(const StreamBuffer& s, long start=0) const
+    long int find(const StreamBuffer& s, ssize_t start=0) const
         {return find(s.buffer+s.offs, s.len, start);}
 
     // startswith: returns true if first size bytes are equal
-    bool startswith(const void* s, long size) const
+    bool startswith(const void* s, size_t size) const
         {return len>=size ? memcmp(buffer+offs, s, size) == 0 : false;}
 
     // startswith: returns true if first string is equal (empty string matches)
@@ -217,9 +218,9 @@ public:
 
 // expand: create copy of StreamBuffer where all nonprintable characters
 // are replaced by <xx> with xx being the hex code of the characters
-    StreamBuffer expand(long start, long length) const;
+    StreamBuffer expand(ssize_t start, ssize_t length) const;
     
-    StreamBuffer expand(long start=0) const
+    StreamBuffer expand(ssize_t start=0) const
         {return expand(start, len);}
 
 // dump: debug function, like expand but also show the 'hidden' memory
@@ -227,4 +228,13 @@ public:
     StreamBuffer dump() const;
 };
 
+// printf size prefix for size_t and ssize_t
+#if defined (__GNUC__) && __GNUC__ >= 3
+#define PRINTF_SIZE_T_PREFIX "z"
+#elif defined (_WIN32)
+#define PRINTF_SIZE_T_PREFIX "I"
+#else
+#define PRINTF_SIZE_T_PREFIX ""
+#endif
+
 #endif
diff --git a/src/StreamCore.cc b/src/StreamCore.cc
index ec821ce..df1524e 100644
--- a/src/StreamCore.cc
+++ b/src/StreamCore.cc
@@ -23,6 +23,8 @@
 #include <ctype.h>
 #include <stdlib.h>
 
+#define S PRINTF_SIZE_T_PREFIX
+
 enum Commands { end_cmd, in_cmd, out_cmd, wait_cmd, event_cmd, exec_cmd,
     connect_cmd, disconnect_cmd };
 const char* commandStr[] = { "end", "in", "out", "wait", "event", "exec",
@@ -983,7 +985,7 @@ readCallback(StreamIoStatus status,
             finishProtocol(ReplyTimeout);
             return 0;
         case StreamIoFault:
-            error("%s: I/O error after reading %ld byte%s: \"%s%s\"\n",
+            error("%s: I/O error after reading %"S"d byte%s: \"%s%s\"\n",
                 name(),
                 inputBuffer.length(), inputBuffer.length()==1 ? "" : "s",
                 inputBuffer.length() > 20 ? "..." : "",
@@ -992,7 +994,7 @@ readCallback(StreamIoStatus status,
             return 0;
     }
     inputBuffer.append(input, size);
-    debug("StreamCore::readCallback(%s) inputBuffer=\"%s\", size %ld\n",
+    debug("StreamCore::readCallback(%s) inputBuffer=\"%s\", size %"S"d\n",
         name(), inputBuffer.expand()(), inputBuffer.length());
     if (*activeCommand != in_cmd)
     {