 | Start a set with this search |
 | Include this search in one of my sets |
 | Exclude this search from one of my sets |
 | Permalink to these results Paste this link in email or IM: |
 | Atom feed for tracking future search results Paste this URL into your reader: |
8 messages in net.java.dev.jna.usersRe: [jna-users] call to sysinfo() cau...| From | Sent On | Attachments |
|---|---|---|
| Joel Uckelman | Apr 7, 2009 8:37 am | |
| Timothy Wall | Apr 7, 2009 8:47 am | |
| Joel Uckelman | Apr 7, 2009 9:05 am | |
| Kevin Burton | Apr 7, 2009 9:56 am | |
| Timothy Wall | Apr 7, 2009 9:58 am | |
| Joel Uckelman | Apr 7, 2009 12:19 pm | |
| Joel Uckelman | Apr 7, 2009 12:22 pm | |
| Kevin Burton | Apr 7, 2009 1:33 pm |
| Permalink for this message Paste this link in email or IM: |
| Permalink for this thread Paste this link in email or IM: |
| Atom feed for this thread Paste this URL into your reader: |
| Subject: | Re: [jna-users] call to sysinfo() causes crash | Actions... |
|---|---|---|
| From: | Joel Uckelman (ucke...@nomic.net) | |
| Date: | Apr 7, 2009 9:05:44 am | |
| List: | net.java.dev.jna.users | |
Thus spake Timothy Wall:
On Apr 7, 2009, at 11:38 AM, Joel Uckelman wrote:
Hi,
I'm trying to call the sysinfo() function from the Linux C library:
int sysinfo(struct sysinfo *info);
struct sysinfo { long uptime; /* Seconds since boot */ unsigned long loads[3]; /* 1, 5, and 15 minute load averages */ unsigned long totalram; /* Total usable main memory size */ unsigned long freeram; /* Available memory size */ unsigned long sharedram; /* Amount of shared memory */ unsigned long bufferram; /* Memory used by buffers */ unsigned long totalswap; /* Total swap space size */ unsigned long freeswap; /* swap space still available */ unsigned short procs; /* Number of current processes */ unsigned long totalhigh; /* Total high memory size */ unsigned long freehigh; /* Available high memory size */ unsigned int mem_unit; /* Memory unit size in bytes */ char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding for libc5 */ };
char _f[] != char*, at least not in the context of a struct. You're only allocating a pointer, when you need a character array.
Aha. That was not clear to me from the documentation. From the C side, there's no difference between char[] and char*, and the JNA docs say to use String for char*.
I changed the last element of the structure on the Java side to be this, to match the definition given in the C header:
public byte[] _f = new byte[20-2*NativeLong.SIZE-Native.getNativeSize(int.class)];
After that, it worked perfectly for me on 32-bit machines, but fails with this exception on 64-bit machines:
Exception in thread "main" java.lang.IllegalArgumentException: Arrays of
length zero not allowed in structure
Two 8-byte longs and one 4-byte int are 20 bytes together, so that makes the byte array _f have zero length on a 64-bit machine. In C, that would just make _f point to the end of the struct.
-- J.