1 files changed, 186 insertions, 0 deletions
diff --git a/prober.py b/prober.py
new file mode 100644
index 0000000..08f5fe0
--- /dev/null
+++ b/prober.py
@@ -0,0 +1,186 @@
+import os.path
+import os
+import subprocess
+import sys
+import distutils.sysconfig
+
+# Set these to None for debugging or subprocess.PIPE to silence compiler
+# warnings and errors.
+STDOUT = subprocess.PIPE
+STDERR = subprocess.PIPE
+# STDOUT = None
+# STDERR = None
+
+# This is the max length that I want a printed line to be.
+MAX_LINE_LENGTH = 78
+
+PYTHON_INCLUDE_DIR = os.path.dirname(distutils.sysconfig.get_config_h_filename())
+#print (PYTHON_INCLUDE_DIR)
+
+def line_wrap_paragraph(s):
+    # Format s with terminal-friendly line wraps.
+    done = False
+    beginning = 0
+    end = MAX_LINE_LENGTH - 1
+    lines = [ ]
+    while not done:
+        if end >= len(s):
+            done = True
+            lines.append(s[beginning:])
+        else:
+            last_space = s[beginning:end].rfind(' ')
+
+            lines.append(s[beginning:beginning + last_space])
+            beginning += (last_space + 1)
+            end = beginning + MAX_LINE_LENGTH - 1
+
+    return lines
+
+
+def print_bad_news(value_name, default):
+    s = "Setup can't determine %s on your system, so it will default to %s which may not be correct." \
+            % (value_name, default)
+    plea = "Please report this message and your operating system info to the package maintainer listed in the README file."
+
+    lines = line_wrap_paragraph(s) + [''] + line_wrap_paragraph(plea)
+
+    border = '*' * MAX_LINE_LENGTH
+
+    s = border + "\n* " + ('\n* '.join(lines)) + '\n' + border
+
+    print (s)
+
+
+def does_build_succeed(filename):
+    # Utility function that returns True if the file compiles and links
+    # successfully, False otherwise.
+    cmd = "cc -Wall -I%s -o ./prober/foo ./prober/%s" %  \
+                (PYTHON_INCLUDE_DIR, filename)
+
+    p = subprocess.Popen(cmd, shell=True, stdout=STDOUT, stderr=STDERR)
+
+    # p.wait() returns the process' return code, so 0 implies that
+    # the compile & link succeeded.
+    return not bool(p.wait())
+
+def compile_and_run(filename, linker_options = ""):
+    # Utility function that returns the stdout output from running the
+    # compiled source file; None if the compile fails.
+    cmd = "cc -Wall -I%s -o ./prober/foo %s ./prober/%s" %  \
+                (PYTHON_INCLUDE_DIR, linker_options, filename)
+
+    p = subprocess.Popen(cmd, shell=True, stdout=STDOUT, stderr=STDERR)
+
+    if p.wait():
+        # uh-oh, compile failed
+        return None
+    else:
+        s = subprocess.Popen(["./prober/foo"],
+                             stdout=subprocess.PIPE).communicate()[0]
+        return s.strip().decode()
+
+
+def sniff_semtimedop():
+    return does_build_succeed("semtimedop_test.c")
+
+
+def sniff_union_semun_defined():
+    # AFAICT the semun union is supposed to be declared in one's code.
+    # However, a lot of legacy code gets this wrong and some header files
+    # define it, e.g.sys/sem.h on OS X where it's #ifdef-ed so that legacy
+    # code won't break. On some systems, it appears and disappears based
+    # on the #define value of _XOPEN_SOURCE.
+    return does_build_succeed("sniff_union_semun_defined.c")
+
+
+def probe_semvmx():
+    # This is the hardcoded default that I chose for two reasons. First,
+    # it's the default on my Mac so I know at least one system needs it
+    # this low. Second, it fits neatly into a 16-bit signed int which
+    # makes me hope that it's low enough to be safe on all systems.
+    semvmx = 32767
+
+    # FIXME -- Ways to get SEMVMX --
+    # 1) Try to compile .c code assuming SEMVMX is #defined
+    # 2) Parse the output from `sysctl kern.sysv.semvmx` (doesn't work
+    #    on OS X).
+    # 3) Parse the output from `ipcs -S`
+    # 4) Run .c code that loops, releasing a semaphore until semop()
+    #    returns ERANGE or the value goes wonky. OS X lets the latter
+    #    happen, which AFAICT is a violation of the spec.
+
+    return semvmx
+
+
+
+def probe_page_size():
+    DEFAULT_PAGE_SIZE = 4096
+
+    page_size = compile_and_run("probe_page_size.c")
+
+    if page_size is None:
+        page_size = DEFAULT_PAGE_SIZE
+        print_bad_news("the value of PAGE_SIZE", page_size)
+
+    return page_size
+
+
+def probe():
+    d = { "KEY_MAX" : "LONG_MAX",
+          "KEY_MIN" : "LONG_MIN"
+        }
+
+    conditionals = [ "_SEM_SEMUN_UNDEFINED" ]
+
+    f = open("VERSION")
+    version = f.read().strip()
+    f.close()
+
+    d["SYSV_IPC_VERSION"] = '"%s"' % version
+    d["PAGE_SIZE"] = probe_page_size()
+    if sniff_semtimedop():
+        d["SEMTIMEDOP_EXISTS"] = ""
+    d["SEMAPHORE_VALUE_MAX"] = probe_semvmx()
+    # Some (all?) Linux platforms #define _SEM_SEMUN_UNDEFINED if it's up
+    # to my code to declare this union, so I use that flag as my standard.
+    if not sniff_union_semun_defined():
+        d["_SEM_SEMUN_UNDEFINED"] = ""
+
+
+
+    msg = """/*
+This header file was generated when you ran setup. Once created, the setup
+process won't overwrite it, so you can adjust the values by hand and
+recompile if you need to.
+
+To recreate this file, just delete it and re-run setup.py.
+
+KEY_MIN, KEY_MAX and SEMAPHORE_VALUE_MAX are stored internally in longs, so
+you should never #define them to anything larger than LONG_MAX.
+*/
+
+"""
+
+    filename = "probe_results.h"
+    if not os.path.exists(filename):
+        lines = [ ]
+
+        for key in d:
+            if key in conditionals:
+                lines.append("#ifndef %s" % key)
+
+            lines.append("#define %s\t\t%s" % (key, d[key]))
+
+            if key in conditionals:
+                lines.append("#endif")
+
+        # A trailing '\n' keeps compilers happy...
+        f = open(filename, "w")
+        f.write(msg + '\n'.join(lines) + '\n')
+        f.close()
+
+    return d
+
+if __name__ == "__main__":
+    s = probe()
+    print (s)